Fixes gcc '-Wunused-but-set-variable' warning:

fs/nfsd/vfs.c: In function 'nfsd_create':
fs/nfsd/vfs.c:1279:16: warning:
 variable 'dirp' set but not used [-Wunused-but-set-variable]
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>