drm/amd/display: Ammend DCPG IP control sequences to align with HW guidance

drm/amd/display: Ammend DCPG IP control sequences to align with HW guidance

[ Upstream commit cbd97d621ece1d92c3542e52f8af7c04cd2c6afb ]

[WHY&HOW]
IP_REQUEST_CNTL should only be toggled off when it was originally, never
unconditionally.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Signed-off-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>