pass -msize-long to sparse on s390

s390 is the only 32bit with unsigned long for size_t (usual for those
is unsigned int).  Tell sparse...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/s390/Makefile

@@ -19,7 +19,7 @@ CFLAGS		+= -m31
 AFLAGS		+= -m31
 UTS_MACHINE	:= s390
 STACK_SIZE	:= 8192
-CHECKFLAGS	+= -D__s390__
+CHECKFLAGS	+= -D__s390__ -msize-long
 else
 LDFLAGS		:= -m elf64_s390
 MODFLAGS	+= -fpic -D__PIC__