drm/i915/dmc: Extract dmc_load_program()

drm/i915/dmc: Extract dmc_load_program()

We'll be needing to reload the program for individual DMCs.
To make that possible pull the code to load the program for
a single DMC into a new function.

This does change the order of things during init/resume
a bit; previously we loaded the program RAM for all DMCs first,
and then loaded the MMIO registers for all DMCs. Now those
operations will be interleaved between different DMCs.

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/20250617170759.19552-5-ville.syrjala@linux.intel.com