fs/compat_rw_copy_check_uvector: add missing compat_ptr call

A call to access_ok is missing a compat_ptr conversion.  Introduced with
b83733639a "compat: factor out
compat_rw_copy_check_uvector from compat_do_readv_writev"

fs/compat.c: In function 'compat_rw_copy_check_uvector':
fs/compat.c:629: warning: passing argument 1 of '__access_ok' makes pointer from integer without a cast

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/compat.c

@@ -626,7 +626,7 @@ ssize_t compat_rw_copy_check_uvector(int type,
 		tot_len += len;
 		if (tot_len < tmp) /* maths overflow on the compat_ssize_t */
 			goto out;
-		if (!access_ok(vrfy_dir(type), buf, len)) {
+		if (!access_ok(vrfy_dir(type), compat_ptr(buf), len)) {
 			ret = -EFAULT;
 			goto out;
 		}