pvr: Transfer optimisation remove unused features from API

pvr: Transfer optimisation remove unused features from API

The transfer command "struct pvr_transfer_cmd" has support for
features not used by Vulkan: colour key, pattern, rop blit and
alpha blending

The whole "struct pvr_transfer_blit" can be removed. Also all code
related to transfer alpha blending can be removed.

This is an optimisation and doesn't fix any dEQP tests.

Signed-off-by: Oskar Rundgren <oskar.rundgren@imgtec.com>
Reviewed-by: Frank Binns <frank.binns@imgtec.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22958>