feat(imx8ulp): add the basic support for idle & system suspned

Add basic support for the cpuidle(cluster retention) and system
suspend support using the HW sleep mode.

When system enter low power mode after doing reboot twice, APD
will be failed to exit from low power mode successfully. it is
because that after secondary reboot, upower will modify the default
power switch config, then DDR will be off wrongly. So config the
low power mode info explicitly before APD entering any low power
mode.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Change-Id: Ib68bfdfd4b925541e343aef4a5296a542451f86b
3 files changed