UKSM: Cleanups

Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>
UKSM: splitting rshash_adjust()

Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>
UKSM: Small cleanup round_update_ladder()

Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>
UKSM: Optimize is_page_full_zero()

memcmp faster in comparison with is_full_zero in several times

Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>