drm: Merge drm_info.c into drm_debugfs.c

Ever since

commit cb6458f97b
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Aug 8 15:41:34 2013 +0200

    drm: remove procfs code, take 2

Having the code shared between procfs and debugfs in the separate
drm_info.c file stopped making sense. Merge them.

Noticed because Lyude asked some questions on irc about why we even
have drm_info_node and I remember this old story.

Cc: Lyude Paul <lyude@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181121213510.31260-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/Makefile

@@ -10,7 +10,7 @@ drm-y       :=	drm_auth.o drm_bufs.o drm_cache.o \
 		drm_scatter.o drm_pci.o \
 		drm_sysfs.o drm_hashtab.o drm_mm.o \
 		drm_crtc.o drm_fourcc.o drm_modes.o drm_edid.o \
-		drm_info.o drm_encoder_slave.o \
+		drm_encoder_slave.o \
 		drm_trace_points.o drm_global.o drm_prime.o \
 		drm_rect.o drm_vma_manager.o drm_flip_work.o \
 		drm_modeset_lock.o drm_atomic.o drm_bridge.o \