drm/amd/display: Update DCN302 SR Exit Latency

[Why&How]
Update SR Exit Latency to fix screen flickering caused due to OTG
underflow. This is the recommended value given by the hardware IP team.

Signed-off-by: Joshua Aberback <joshua.aberback@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>