drm/i915/adl_p: Pipe B DMC Support

ADLP requires us to load both Pipe A and Pipe B.
Plug Pipe B loading support.

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210621191415.29823-4-anusha.srivatsa@intel.com