drm/i915: Define the "unmodified vblank" interrupt bit

On TGL+ the normal "start of vblank" interrupt is the pipe's
(potentially delayed) version. Add the new bit for the
transcoder's "unmodified" vblank so I don't have to dig it
out from bspec every time.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230213225258.2127-7-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/i915_reg.h

@@ -5387,6 +5387,7 @@
 #define  GEN8_PIPE_CDCLK_CRC_DONE	(1 << 28)
 #define  XELPD_PIPE_SOFT_UNDERRUN	(1 << 22)
 #define  XELPD_PIPE_HARD_UNDERRUN	(1 << 21)
+#define  GEN12_PIPE_VBLANK_UNMOD	(1 << 19)
 #define  GEN8_PIPE_CURSOR_FAULT		(1 << 10)
 #define  GEN8_PIPE_SPRITE_FAULT		(1 << 9)
 #define  GEN8_PIPE_PRIMARY_FAULT	(1 << 8)