MLK-18502-02 plat: imx8mm: keep L2 cache memory power in WAIT mode

When system enter deepest cpuilde(WAIT mode), the L2 cache memory
can be on for retention to increase the system performance. So
the WAIT mode with cluster power down should be defined as
rentention power state in PSCI. changing the WAIT_OFF_STATE to
WAIT_RET_STATE to make sure the l2 cache memory is not
clean & invalidate.

Signed-off-by: Bai Ping <>
(cherry picked from commit 7f83fd077208220c57a389871abb987d371ca50c)
3 files changed