graphics/mesa-dri: Convert gallium and vulkan driver to port options

Instead of selecting the one by arches add options.
This will help users who doesn't want some features.
The default are still the same based on the specific arch.
No functional changes intended.

Differential Revision: https://reviews.freebsd.org/D45754
Inspired by: graphics/mesa-devel
Reviewed by: bapt
Sponsored by: Beckhoff Automation GmbH & Co. KG