drm/i915: Dump PGTBL_ER on gen2/3/4 error interrupt

PGTBL_ER contains the individual reasons for the page table
error interrupt. Dump it out.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230125185234.21599-4-ville.syrjala@linux.intel.com


Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>