drm/i915/rkl: Handle new DPCLKA_CFGCR0 layout

RKL uses a slightly different bit layout for the DPCLKA_CFGCR0 register.

v2:
 - Fix inverted mask application when updating ICL_DPCLKA_CFGCR0
 - Checkpatch style fixes

Bspec: 50287
Cc: Aditya Swarup <aditya.swarup@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200716220551.2730644-2-matthew.d.roper@intel.com


Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>