drm/amd/display: Fix pflip IRQ status after gpu reset.

Problem:
After GPU reset pflip completion IRQ is disabled and hence
any subsequent mode set or plane update leads to hang.

Fix:
Unless acrtc->otg_inst is initialized to -1 during display
block initializtion then durng resume from GPU reset
amdgpu_irq_gpu_reset_resume_helper will override CRTC 0 pflip
IRQ value with whatever value was on every other unused CRTC because
dm_irq_state will do irq_source = dal_irq_type + acrtc->otg_inst
where acrtc->otg_inst will be 0 for every unused CRTC.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -3424,6 +3424,7 @@ static int amdgpu_dm_crtc_init(struct amdgpu_display_manager *dm,
 
 	acrtc->crtc_id = crtc_index;
 	acrtc->base.enabled = false;
+	acrtc->otg_inst = -1;
 
 	dm->adev->mode_info.crtcs[crtc_index] = acrtc;
 	drm_crtc_enable_color_mgmt(&acrtc->base, MAX_COLOR_LUT_ENTRIES,