feat(imx8ulp): add a flag check for the ddr status

for some user case, the ddr may need to be controlled
by RTD side to save power, when APD resume from low
power mode, it should wait ddr is ready for access.
currently we use a GPR in SIM_RTD_SEC as a flag to
indicate when the DDR is for access, non-zero value
means the DDR can be access from APD.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Change-Id: I6fb0cc17a040d803a597304620202423f646f294
1 file changed