checkpatch: exclude asm volatile from complex macro check

asm volatile and all its variants like __asm__ __volatile__ ("<foo>")
are reported as errors with "Macros with with complex values should be
enclosed in parentheses".

Make an exception for these asm volatile macro definitions by converting
the "asm volatile" to "asm_volatile" so it appears as a single function
call and the error isn't reported.

Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Jeff Merkey <linux.mdb@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>