btrfs: zoned: use local fs_info variable in btrfs_load_block_group_dup()

btrfs: zoned: use local fs_info variable in btrfs_load_block_group_dup()

btrfs_load_block_group_dup() has a local pointer to fs_info, yet the
error prints dereference fs_info from the block_group.

Use local fs_info variable to make the code more uniform.

Reviewed-by: Daniel Vacek <neelx@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>