gen7 fbo: make unmatched depth/stencil configs return unsupported

gen7 fbo: make unmatched depth/stencil configs return unsupported

For gen >= 7, we will use the lod/minimum-array-element fields to
support layered rendering. This means that we must restrict
the depth & stencil attachments to match in various more retrictive
ways. (Now the width, height, depth, LOD and layer must match)

The reason width, height, and depth must match is that the hardware
has a single set of width, height, and depth settings (in
3DSTATE_DEPTH_BUFFER) that affect both the depth and stencil buffers.
Since these controls determine the miptree layout, they need to be
set correctly in order for lod and minimum-array-element to work
properly.  So the only way rendering can work is if the width,
height, and depth match.

In the future, if this restriction proves to be a problem (say
because some crucial client application relies on rendering to
different levels/layers of stencil and depth buffers), then we can
always work around the restriction by copying depth and/or stencil
data to a temporary buffer prior to rendering (much in the same way
that brw_workaround_depthstencil_alignment() does today for
gen < 7), but hopefully that won't be necessary.

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Paul Berry <stereotype441@gmail.com>