ext4: save all error info in save_error_info() and drop ext4_set_errno()

Using a separate function, ext4_set_errno() to set the errno is
problematic because it doesn't do the right thing once
s_last_error_errorcode is non-zero.  It's also less racy to set all of
the error information all at once.  (Also, as a bonus, it shrinks code
size slightly.)

Link: https://lore.kernel.org/r/20200329020404.686965-1-tytso@mit.edu
Fixes: 878520ac45 ("ext4: save the error code which triggered...")
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/indirect.c

@@ -1019,7 +1019,7 @@ static void ext4_free_branches(handle_t *handle, struct inode *inode,
 			 * (should be rare).
 			 */
 			if (!bh) {
-				EXT4_ERROR_INODE_BLOCK(inode, nr,
+				ext4_error_inode_block(inode, nr, EIO,
 						       "Read failure");
 				continue;
 			}