UBIFS: make ubifs_lpt_init clean-up in case of failure

Most functions in UBIFS follow the following designn pattern: if the function
allocates multiple resources, and failss at some point, it frees what it has
allocated and returns an error. So the caller can rely on the fact that the
callee has cleaned up everything after own failure.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Acked-by: Sidney Amani <seed95@gmail.com>