checkpatch: add checks for constant non-octal permissions

umode_t permissions are sometimes mistakenly written with decimal
constants.  Verify that numeric permissions are using octal.

Add a list of the most commonly used functions and macros that have
umode_t permissions and the argument position.

Add a $Octal type to $Constant.
Allow $LvalOrFunc to be a pointer indirection too.

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