anv/clear: Clear E5B9G9R9 images as R32_UINT

anv/clear: Clear E5B9G9R9 images as R32_UINT

We can't actually clear these images normally because we can't render to
them.  Instead, we have to manually unpack the rgb9e5 color value on the
CPU and clear it as R32_UINT.  We still have a bit of work to do to clear
non-power-of-two images, but this should get all of the power-of-two clears
working on at least Haswell.  This fixes three of the new Vulkan CTS tests
in the dEQP-VK.api.image_clearing.clear_color_image.* group.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Nanley Chery <nanley.g.chery@intel.com>
Cc: "12.0" <mesa-stable@lists.freedesktop.org>