anv: don't require render target isl bit for depth/stencil surfaces

anv: don't require render target isl bit for depth/stencil surfaces

Blorp can deal with depth/stencil surfaces blits/copies without the
render target requirement. Also having both render target and
depth/stencil requirement is incompatible from isl's point of view.

This fixes an image creation issue in the high level quality settings
of the Unity3D player, which requires a depth texture with src/dst
transfer & 4x multisampling.

v2: Simply aspect checking condition (Jason)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Cc: 13.0 17.0 <mesa-stable@lists.freedesktop.org>