sync_bitops: fix wrong comments [Bug 10247]

Fix wrong function name and references to non-x86 architectures.

Signed-off-by: Matti Linnanvuori <mattilinnanvuori@yahoo.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>