checkpatch: warn when formats use %Z and suggest %z

vsnprintf extension %Z<foo> is non-standard C.  Suggest the use of %z
instead.

Miscellanea:

 - Correct the misuse of type string PRINTF_0xDECIMAL type strings are
   supposed to be uppercase only. Fix this and add tr/[a-z]/[A-Z] to the
   type check in case I forget this again sometime in the future.

 - Improve the mechanism to find these defects so all 3 current checks
   are done on the format string

[joe@perches.com: correct the misuse of type string PRINTF_0xDECIMAL, improve the mechanism to find these defects]
  Link: http://lkml.kernel.org/r/4e3ad74b0c9dc229b06018a2d79655308ddbbebd.1484014173.git.joe@perches.com
Link: http://lkml.kernel.org/r/20170109235955.GA6787@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
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>