nvidia-drm-kmod: Update with fix for PRIME

This updates the nvidia-drm ports to contain the fix for
https://github.com/amshafer/nvidia-driver/issues/20

Also updates the port Makefiles to use CONFLICTS_INSTALL to resolve
PR 273261, and adds PORTREVISION to the github tag referenced.

Differential Revision: https://reviews.freebsd.org/D41591

PR:		273261
Tested by:	arrowd