drm/i915/dmc: Assert DMC is loaded harder

drm/i915/dmc: Assert DMC is loaded harder

Currently we have some asserts to make sure the main DMC has been
loaded. Add similar asserts for the pipe DMCs. And we might as well
just check all the mmio registers the firmware has asked us to
initialize. That also covers the hardcoded SSP/HTP registers we were
checking for the main DMC.

TODO: Maybe always configure DMC_EVT_CTL_ENABLE the way the firmware
      has it set so that we wouldn't need to special case in the assert?

v2: Also assert in intel_dmc_load_program()

Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250617170759.19552-8-ville.syrjala@linux.intel.com