checkpatch: don't check c99 types like uint8_t under tools

Tools contains user space code so uintX_t types are just fine.

Link: http://lkml.kernel.org/r/1479286379-853-1-git-send-email-tomas.winkler@intel.com
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Acked-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>