reiserfs: Fix spurious unlock in reiserfs_fill_super() error handling

[ Upstream commit 4d5c1ada ]

When we fail to allocate string for journal device name we jump to
'error' label which tries to unlock reiserfs write lock which is not
held. Jump to 'error_unlocked' instead.

Fixes: f32485be ("reiserfs: delay reiserfs lock until journal initialization")
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>