drm/i915: pass dev_priv explicitly to HSW_TVIDEO_DIP_GCP

Avoid the implicit dev_priv local variable use, and pass dev_priv
explicitly to the HSW_TVIDEO_DIP_GCP register macro.

Reviewed-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/36f0b90f07c7aa78e88fadb375359df39ecd0a77.1716808214.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>