drm/i915/switcheroo: use struct drm_device based logging

Convert all the pr_* logging macros to the struct drm_device based
macros to provide device specific logging.

No functional changes.

Cc: Wambui Karuga <wambui.karugax@gmail.com>
Reviewed-by: Wambui Karuga <wambui.karugax@gmail.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200402114819.17232-9-jani.nikula@intel.com