locking: Allow arch-inlined spinlocks

This allows an architecture to specify per lock variant if the
locking code should be kept out-of-line or inlined.

If an architecure wants out-of-line locking code no change is
needed. To force inlining of e.g. spin_lock() the line:

  #define __always_inline__spin_lock

needs to be added to arch/<...>/include/asm/spinlock.h

If CONFIG_DEBUG_SPINLOCK or CONFIG_GENERIC_LOCKBREAK are
defined the per architecture defines are (partly) ignored and
still out-of-line spinlock code will be generated.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Horst Hartmann <horsth@linux.vnet.ibm.com>
Cc: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Miller <davem@davemloft.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: <linux-arch@vger.kernel.org>
LKML-Reference: <20090831124418.375299024@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>