ubifs: Call ubifs_iput when ubifs_iget is used

The inode should be freed after a reference is get to avoid
memory leak

Tested-by: Alexander Dahl <ada@thorsis.com>
Link: https://lore.kernel.org/u-boot/b698ec3e-d857-6512-8cc9-4edcab0a41b9@denx.de/T/#t
Link: https://lore.kernel.org/all/8f3a7059-6330-f332-8e9f-729b853e001e@denx.de/T/


Co-developed-by: Heiko Schocher <hs@denx.de>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>