drm/i915/dp: Do not set master_trans bit in bitmak if INVALID_TRANSCODER

In the port sync mode, for the master crtc, the master_transcoder is INVALID.
In that case since its value is -1, do not set the bit in the bitmask.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Fixes: d0eed154 ("drm/i915: Fix post-fastset modeset check for port sync")
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200123002415.31478-1-manasi.d.navare@intel.com

drivers/gpu/drm/i915/display/intel_display.c

@@ -14649,8 +14649,10 @@ static int intel_atomic_check(struct drm_device *dev,
 		}
 
 		if (is_trans_port_sync_mode(new_crtc_state)) {
-			u8 trans = new_crtc_state->sync_mode_slaves_mask |
-				   BIT(new_crtc_state->master_transcoder);
+			u8 trans = new_crtc_state->sync_mode_slaves_mask;
+
+			if (new_crtc_state->master_transcoder != INVALID_TRANSCODER)
+				trans |= BIT(new_crtc_state->master_transcoder);
 
 			if (intel_cpu_transcoders_need_modeset(state, trans)) {
 				new_crtc_state->uapi.mode_changed = true;