fs/bio.c: add missing __user annotation

As reported by sparse:

fs/bio.c:720:13: warning: incorrect type in assignment (different address spaces)
fs/bio.c:720:13:    expected char *iov_addr
fs/bio.c:720:13:    got void [noderef] <asn:1>*
fs/bio.c:724:36: warning: incorrect type in argument 2 (different address spaces)
fs/bio.c:724:36:    expected void const [noderef] <asn:1>*from
fs/bio.c:724:36:    got char *iov_addr

Signed-off-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

fs/bio.c

@@ -722,7 +722,7 @@ static int __bio_copy_iov(struct bio *bio, struct bio_vec *iovecs,
 
 		while (bv_len && iov_idx < iov_count) {
 			unsigned int bytes;
-			char *iov_addr;
+			char __user *iov_addr;
 
 			bytes = min_t(unsigned int,
 				      iov[iov_idx].iov_len - iov_off, bv_len);