ext4: mballoc: simplify error handling in ext4_init_mballoc()

This patch simplifies error handling logic in ext4_init_mballoc(),
by adding all the cleanups at one place at the end of that function.

There should be no functionality change in this patch.

Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/r/8621a7bc68f7107a9ac4292afeb784515333bd25.1589086800.git.riteshh@linux.ibm.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>