checkpatch: find hex constants as a single IDENT

Hexadecimal values are current found in 2 parts.  A hex constant like
0x123456abcdef is found as 0 and then x123456abcdef and later coalesced.

Instead, reverse the order of the 2 searches in $Constant to find 0x
first, then 0 so that the entire hex constant is found all at once.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>