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
(cherry picked from commit bddc1891)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>