Reduce drm text size ~1% by using drm_err and
printf extension %pV to emit error messages.

Remove unused macro DRM_MEM_ERROR.

$ size drivers/gpu/drm/built-in.o*
   text	   data	    bss	    dec	    hex	filename
 361159	   9663	    256	 371078	  5a986	drivers/gpu/drm/built-in.o.new
 365416	   9663	    256	 375335	  5ba27	drivers/gpu/drm/built-in.o.old

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>