drm/i915: Bump gen7+ fb size limits to 16kx16k

With gtt remapping in place we can use arbitrarily large
framebuffers. Let's bump the limits to 16kx16k on gen7+.
The limit was chosen to match the maximum 2D surface size
of the 3D engine.

With the remapping we could easily go higher than that for the
display engine. However the modesetting ddx will blindly assume
it can handle whatever is reported via kms. The oversized
buffer dimensions are not caught by glamor nor Mesa until
finally an assert will trip when genxml attempts to pack the
SURFACE_STATE. So we pick a safe limit to avoid the X server
from crashing (or potentially misbehaving if the genxml asserts
are compiled out).

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110187


Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190509122159.24376-9-ville.syrjala@linux.intel.com


Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>