x86: Clean up late e820 resource allocation

This makes the late e820 resources use 'insert_resource_expand_to_fit()'
instead of doing a 'reserve_region_with_split()', and also avoids
marking them as IORESOURCE_BUSY.

This results in us being perfectly happy to use pre-existing PCI
resources even if they were marked as being in a reserved region, while
still avoiding any _new_ allocations in the reserved regions.  It also
makes for a simpler and more accurate resource tree.

Example resource allocation from Jonathan Corbet, who has firmware that
has an e820 reserved entry that covered a big range (e0000000-fed003ff),
and that had various PCI resources in it set up by firmware.

With old kernels, the reserved range would force us to re-allocate all
pre-existing PCI resources, and his reserved range would end up looking
like this:

	e0000000-fed003ff : reserved
	  fec00000-fec00fff : IOAPIC 0
	  fed00000-fed003ff : HPET 0

where only the pre-allocated special regions (IOAPIC and HPET) were kept
around.

With 2.6.28-rc2, which uses 'reserve_region_with_split()', Jonathan's
resource tree looked like this:

	e0000000-fe7fffff : reserved
	fe800000-fe8fffff : PCI Bus 0000:01
	 fe800000-fe8fffff : reserved
	fe900000-fe9d9aff : reserved
	fe9d9b00-fe9d9bff : 0000:00:1f.3
	 fe9d9b00-fe9d9bff : reserved
	fe9d9c00-fe9d9fff : 0000:00:1a.7
	 fe9d9c00-fe9d9fff : reserved
	fe9da000-fe9dafff : 0000:00:03.3
	 fe9da000-fe9dafff : reserved
	fe9db000-fe9dbfff : 0000:00:19.0
	 fe9db000-fe9dbfff : reserved
	fe9dc000-fe9dffff : 0000:00:1b.0
	 fe9dc000-fe9dffff : reserved
	fe9e0000-fe9fffff : 0000:00:19.0
	 fe9e0000-fe9fffff : reserved
	fea00000-fea7ffff : 0000:00:02.0
	 fea00000-fea7ffff : reserved
	fea80000-feafffff : 0000:00:02.1
	 fea80000-feafffff : reserved
	feb00000-febfffff : 0000:00:02.0
	 feb00000-febfffff : reserved
	fec00000-fed003ff : reserved
	 fec00000-fec00fff : IOAPIC 0
	 fed00000-fed003ff : HPET 0

and because the reserved entry had been split and moved into the
individual resources, and because it used the IORESOURCE_BUSY flag, the
drivers that actually wanted to _use_ those resources couldn't actually
attach to them:

	e1000e 0000:00:19.0: BAR 0: can't reserve mem region [0xfe9e0000-0xfe9fffff]
	HDA Intel 0000:00:1b.0: BAR 0: can't reserve mem region [0xfe9dc000-0xfe9dffff]

with this patch, the resource tree instead becomes

	e0000000-fed003ff : reserved
	  fe800000-fe8fffff : PCI Bus 0000:01
	  fe9d9b00-fe9d9bff : 0000:00:1f.3
	  fe9d9c00-fe9d9fff : 0000:00:1a.7
	    fe9d9c00-fe9d9fff : ehci_hcd
	  fe9da000-fe9dafff : 0000:00:03.3
	  fe9db000-fe9dbfff : 0000:00:19.0
	    fe9db000-fe9dbfff : e1000e
	  fe9dc000-fe9dffff : 0000:00:1b.0
	    fe9dc000-fe9dffff : ICH HD audio
	  fe9e0000-fe9fffff : 0000:00:19.0
	    fe9e0000-fe9fffff : e1000e
	  fea00000-fea7ffff : 0000:00:02.0
	  fea80000-feafffff : 0000:00:02.1
	  feb00000-febfffff : 0000:00:02.0
	  fec00000-fec00fff : IOAPIC 0
	  fed00000-fed003ff : HPET 0

ie the one reserved region now ends up surrounding all the PCI resources
that were allocated inside of it by firmware, and because it is not
marked BUSY, drivers have no problem attaching to the pre-allocated
resources.

Reported-and-tested-by: Jonathan Corbet <corbet@lwn.net>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Robert Hancock <hancockr@shaw.ca>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>