Kbuild: Disable the -Wformat-security gcc flag

Some distributions have enabled the gcc flag -Wformat-security by default.
This results in a number of warnings about format arguments to functions,
sometimes in cases where fixing the warning is not likely to actually fix a
bug.  Instead of hand patching a dozens of places (possibly more) that produce
warnings that get ignored anyway we just turn off the flag in the Makefile.
Signed-off-by: Floris Kraak <randakar@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

Makefile

@@ -344,7 +344,8 @@ KBUILD_CPPFLAGS := -D__KERNEL__
 
 KBUILD_CFLAGS   := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
 		   -fno-strict-aliasing -fno-common \
-		   -Werror-implicit-function-declaration
+		   -Werror-implicit-function-declaration \
+		   -Wno-format-security
 KBUILD_AFLAGS   := -D__ASSEMBLY__
 
 # Read KERNELRELEASE from include/config/kernel.release (if it exists)