MLK-17795: drm: imx: hdp: Fix 10-bit to 8-bit color depth switch on iMX8MQ

MLK-17795: drm: imx: hdp: Fix 10-bit to 8-bit color depth switch on iMX8MQ

When switching from a 10-bit to an 8-bit color depth, the PHY pixel engine
simply stops functioning correctly 90% of the time. This results in the
HDMI sink not detecting any signal.

This patch will reset the PHY pixel engine after the pipe clocks are ON,
in the bridge enable callback. This will make the pixel engine work
correctly when BPC changes. Resetting the pixel engine before all the pipe
clocks are on, produces no results.

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@nxp.com>
(cherry picked from commit 72246ac9ccfa2074f4f575292af10d19a58c95c4)