MLK-22207 plat: imx8m: Fix the data sync issue in dram dvfs flow

Explict memory barrier(DSB) is necessary to make sure
other cores observe the correct flags updated by the primary
core before the primary begins doing DRAM DVFS.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
(cherry picked from commit dac8d677447c153cd148fee9e35445c24162f190)
1 file changed