On skl the crc registers were extended to provide plane crcs
for up to 7 planes. Add the new crc sources.

The current code uses the ivb+ register definitions for skl+
which does happen to work as the plane1, plane2, and dmux/pf
bits happen the match what ivb+ had. So no bug in the current
code.

v2: Drop the unused set_wa parameter (DK)
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190214192219.3858-4-ville.syrjala@linux.intel.comReviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>