nfsd warning fix

gcc-4.3:

fs/nfsd/nfsctl.c: In function 'write_getfs':
fs/nfsd/nfsctl.c:248: warning: cast from pointer to integer of different size

Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>