drivers/staging/lustre: Fix set-but-unused whinge.

drivers/staging/lustre/lustre/fid/lproc_fid.c: In function 'ldebugfs_fid_write_common':
drivers/staging/lustre/lustre/fid/lproc_fid.c:67:6: warning: variable 'rc' set but not used [-Wunused-but-set-variable]
  int rc;

We fix it by *using* the return code to help bulletproof it.  It says it's
test code - it should be *more* bulletproof than production, not less.
Signed-off-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/fid/lproc_fid.c

@@ -85,6 +85,8 @@ ldebugfs_fid_write_common(const char __user *buffer, size_t count,
 	rc = sscanf(kernbuf, "[%llx - %llx]\n",
 		    (unsigned long long *)&tmp.lsr_start,
 		    (unsigned long long *)&tmp.lsr_end);
+	if (rc != 2)
+		return -EINVAL;
 	if (!range_is_sane(&tmp) || range_is_zero(&tmp) ||
 	    tmp.lsr_start < range->lsr_start || tmp.lsr_end > range->lsr_end)
 		return -EINVAL;