Get vma from mmap and insert it to extent
Add bankshot2_evict_extent
Retry alloc blocks after remove extent. There is bug when rerun application.
bankshot2_write_back_extent
Use list instead of array for vma list
Add ioctl remove mapping
Use find_data_block instead of get_xip_mem in write_back_extent
unmap mappings when remove them. Also add some debug info.