drm/via: Update to the latest via_3d_reg header

Updated the 3d_reg header file to match what is used by the openchrome
driver.
This verifies that the two drivers can use the same header file.

The file is a verbatim copy from the openchrome repo - a few style
issues will be fixed in following commits.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Kevin Brace <kevinbrace@bracecomputerlab.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220713170202.1798216-11-sam@ravnborg.org