drm/i915/ggtt: use new drm logging macros in gt/intel_ggtt.c

Manual conversion of the printk based logging macros to the new struct
drm_based logging macros in drm/i915/gt/intel_ggtt.c.
Also includes extracting the struct drm_i915_private device from various
intel types to use in the new macros.

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/20200128071437.9284-3-wambui.karugax@gmail.com