drm/i915/pch: convert to using the drm_dbg_kms() macro.

Convert the use of the DRM_DEBUG_KMS() logging macro to the new struct
drm_device based drm_dbg_kms() logging macro in i915/intel_pch.c.

Signed-off-by: Wambui Karuga <wambui.karugax@gmail.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b79ee0f6efbf8358cbb4f2e163fa6b5bb04db794.1578409433.git.wambui.karugax@gmail.com