drm/via: Embed via_irq in via_dri1

All functions are made static as there are no more external users.
The file had new copyrights that are kept.

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/20220713170202.1798216-7-sam@ravnborg.org