graphics/drm-515-kmod: add extra patch to unbreak on 15 and newer

Conditionally apply a patch to avoid conflicts with an updated LinuxKPI.
This should make this port both build and work again.
The patch is conditional for the moment as 14.3-R and stable/14 do not
have the LinuxKPI changes yet. stable/14 will likely get it before
14.4-R. At that point it might be easier to (a) have it conditional
in the drm-kmod branch based on __FreeBSD_version or (b) have a
backout patch here for 14.2-R and stable/14 before the LinuxKPI update.

PR: 290432
Reported by: kargl