drm/i915: Clean up dbuf debugs during .atomic_check()

drm/i915: Clean up dbuf debugs during .atomic_check()

Combine the two per-pipe dbuf debugs into one, and use the canonical
[CRTC:%d:%s] style to identify the crtc. Also use the same style as
the plane code uses for the ddb start/end, and prefix bitmask properly
with 0x to make it clear they are in fact bitmasks.

The "how many total slices we are going to use" debug we move to
outside the crtc loop so it gets printed only once at the end.

Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200225171125.28885-12-ville.syrjala@linux.intel.com
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>