agp: Remove trailing whitespaces

Trivial coding-style fix.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Helge Deller <deller@gmx.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20211201114645.15384-2-tzimmermann@suse.de