pvr: Improve support for image clears

pvr: Improve support for image clears

Depth/stencil surfaces are not PBE renderable, so a compatible format must
be used instead. The code to calculate this compatible format was not called
when configuring the PBE, and it was missing formats.

Also the code to calculate PBE swizzles was throwing an error in unhandled
cases, rather than using the pre-calculated defaults which was the correct
behaviour.

Fixes blits in dEQP-VK.draw.renderpass.depth_clamp.d32_sfloat

Signed-off-by: James Glanville <james.glanville@imgtec.com>
Signed-off-by: Karmjit Mahil <Karmjit.Mahil@imgtec.com>
Reviewed-by: Frank Binns <frank.binns@imgtec.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22748>