After src commit 33595d4ae01c added pci_map_rom() and pci_unmap_rom() to
linuxkpi, graphics/drm-latest-kmod failed to build because drm-kmod
defined the same macros itself.

Upstream drm-kmod made its definitions conditional, and ports commit
7e420adaf6ef pulled that fix in for drm-515-kmod, drm-61-kmod,
drm-66-kmod, and drm-612-kmod. drm-latest-kmod was missed, so move it
to the same tag as drm-612-kmod.

Bump PORTREVISION of the nvidia-drm-latest-kmod ports, which build
against the drm-kmod sources, and update their distinfo for the new
tarball.

Reference: https://github.com/freebsd/drm-kmod/pull/503