Since commit fe7c36c7 ("Makefile: Build with -Werror=date-time if
the compiler supports it"), use of __DATE__, __TIME__, and __TIMESTAMP__
has not been allowed.

As this test is gcc version specific (> 4.9), it hasn't prevented a few
new uses from creeping into the kernel sources.

Make checkpatch complain about them.
Signed-off-by: NJoe Perches <joe@perches.com>
Original-patch-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>