drm/amd: Add a DC debug mask for IPS

For debugging IPS-related issues, expose a new debug mask
that allows to disable IPS.
Usage:
amdgpu.dcdebugmask=0x800

Signed-off-by: Roman Li <Roman.Li@amd.com>
Tested-by: Mark Broadworth <mark.broadworth@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Roman Li

drivers/gpu/drm/amd/include/amd_shared.h

@@ -258,6 +258,7 @@ enum DC_DEBUG_MASK {
 	DC_ENABLE_DML2 = 0x100,
 	DC_DISABLE_PSR_SU = 0x200,
 	DC_DISABLE_REPLAY = 0x400,
+	DC_DISABLE_IPS = 0x800,
 };
 
 enum amd_dpm_forced_level;