btrfs: simplify the no-bioc fast path condition in btrfs_map_block

nr_alloc_stripes can't be one if we are writing to a replacement device,
as it is incremented for that case right above.  Remove the duplicate
checks.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -6432,9 +6432,7 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
 	 * I/O context structure.
 	 */
 	if (smap && num_alloc_stripes == 1 &&
-	    !((map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) && mirror_num > 1) &&
-	    (op == BTRFS_MAP_READ || !dev_replace_is_ongoing ||
-	     !dev_replace->tgtdev)) {
+	    !((map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) && mirror_num > 1)) {
 		set_io_stripe(smap, map, stripe_index, stripe_offset, stripe_nr);
 		if (mirror_num_ret)
 			*mirror_num_ret = mirror_num;