drm/amd/display: Do not clear GPINT register when releasing DMUB from reset

[Why & How]
There's no need to clear GPINT register for DMUB
when releasing it from reset. Fix that.

Fixes: ac2e555e

 ("drm/amd/display: Add DMCUB source files and changes for DCN32/321")
Reviewed-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>