drm/i915/xelpd: Pipe A DMC plugging

This patch adds Pipe A plumbing to the already
existing parsing and loading functions which is
taken care of in the prep patches. Adding MAX_DMC_FW
to keep track for both Main and Pipe A DMC while loading
the respective blobs.

Also adding present field in dmc_info.
s/find_dmc_fw_offset/csr_set_dmc_fw_offset. While at it add
fw_info_matches_stepping() helper. CSR_PROGRAM() should now
take the starting address of the particular blob (Main or Pipe)
and not hardcode it.

v2: Add dmc_offset and start_mmioaddr fields for dmc_info struct.

v3: Add a missing corner cases of stepping-substepping combination in
fw_info_matches_stepping() helper.

v4: Add macro for start_mmioaddr for V1 package. Simplify code
in dmc_set_fw_offset (Lucas)

Cc: Souza, Jose <jose.souza@intel.com>
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/20210621191415.29823-3-anusha.srivatsa@intel.com