swrast_kms: use swkmsDRI2Extension instead of driDRI2Extension

This set of changes:
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15649

caused a regression in Xorg when using swrast_kms:
   (EE) AIGLX error: Calling driver entry point failed

This commit changes the swrast_kms driver to use a dedicated screen init function
(which I believe was overlooked); I also took the opportunity to rename the
associated plumbling to have swrast-specific names.

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16942>
4 files changed