drm/i915/mtl: Add the missing CPU transcoder mask in intel_device_info

CPU transcoder mask is used to iterate over the available
CPU transcoders in the macro for_each_cpu_transcoder().

The macro is broken on MTL and got highlighted when audio
state was being tracked for each transcoder added in [1].

Add the missing CPU transcoder mask which is similar to ADL-P
mask but without DSI transcoders.

[1]: https://patchwork.freedesktop.org/patch/523723/

Fixes: 78353039 ("drm/i915/mtl: Add MeteorLake PCI IDs")
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Acked-by: Haridhar Kalvala <haridhar.kalvala@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230420221248.2511314-1-radhakrishna.sripada@intel.com

drivers/gpu/drm/i915/i915_pci.c

@@ -1134,6 +1134,8 @@ static const struct intel_gt_definition xelpmp_extra_gt[] = {
 static const struct intel_device_info mtl_info = {
 	XE_HP_FEATURES,
 	XE_LPDP_FEATURES,
+	.__runtime.cpu_transcoder_mask = BIT(TRANSCODER_A) | BIT(TRANSCODER_B) |
+			       BIT(TRANSCODER_C) | BIT(TRANSCODER_D),
 	/*
 	 * Real graphics IP version will be obtained from hardware GMD_ID
 	 * register.  Value provided here is just for sanity checking.