exofs: Fix bio leak in error handling path (sync read)

When failing a read request in the sync path, called from
write_begin, I forgot to free the allocated bio, fix it.

Signed-off-by: Boaz Harrosh <[e-mail]>

fs/exofs/inode.c

···
 err:
 	if (!is_sync)
 		_unlock_pcol_pages(pcol, ret, READ);
+	else /* Pages unlocked by caller in sync mode only free bio */
+		pcol_free(pcol);
+
 	kfree(pcol_copy);
 	if (or)
 		osd_end_request(or);