ext4: fix error handling in ext4_create_journal

Fix error handling in ext4_create_journal according to kernel conventions.

Signed-off-by: Borislav Petkov <bbpetkov@yahoo.de>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>