drm/i915: Drop usless master_transcoder assignments

The entire crtc state has been reset before readout so
master_transcoder is already set to INVALID.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200313164831.5980-4-ville.syrjala@linux.intel.com


Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>