drm/i915/dmc: improve firmware parse failure propagation

drm/i915/dmc: improve firmware parse failure propagation

Return failures from parse_dmc_fw() instead of relying on
intel_dmc_has_payload(). Handle and error report them slightly better,
including a new error message for when the firmware does not contain the
main program.

v2: Print specific error message for payload not found (Gustavo)

Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Acked-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/18833681978ec3ac779cce943221cc5b532c7c45.1713519628.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>