drm/amd/display: Always exit DMCUB idle when called

[Why]
dc->idle_optimizations_allowed may be desynced with the hardware state.

[How]
Make sure we always exit out when dc_dmub_srv_exit_low_power_state is
called by removing the check.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Sung joon Kim <sungjoon.kim@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>