rtc-cmos: export second NVRAM bank

Teach rtc-cmos about the second bank of registers found on most modern x86
systems, giving access to 128 bytes more NVRAM.

This version only sees that extra NVRAM when both register banks are
provided as part of *one* PNP resource.  Since BIOS on some systems
presents them using two IO resources, and nothing merges them, this can't
always show all the NVRAM.  (We're supposed to be able to use PNP id
PNP0b01 too, but BIOS tables doesn't often seem to use that particular
option.)

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>