Missing include file in kallsyms.h

The Build with randconfig fails with following error with the
2.6.24-rc4-git9

include/linux/kallsyms.h:56: error: `NULL' undeclared (first use in this
function)
include/linux/kallsyms.h:56: error: (Each undeclared identifier is
reported only once
include/linux/kallsyms.h:56: error: for each function it appears in.)
make[2]: *** [arch/powerpc/platforms/cell/spu_callbacks.o] Error 1
make[1]: *** [arch/powerpc/platforms/cell] Error 2
make: *** [arch/powerpc/platforms] Error 2

Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>