mtd: sm_ftl: Fix memory leak in sm_init_zone() error path

In sm_init_zone(), 'zone->lba_to_phys_table' is allocated through
kmalloc_array() and 'zone->free_sectors' is allocated in kfifo_alloc()
respectively. However, they are not deallocated in the following execution
if sm_read_sector() fails, leading to memory leaks. To fix this issue, free
them before returning -EIO.

Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
Signed-off-by: Richard Weinberger <richard@nod.at>