graphics/nvidia-drm-*-kmod*: Bump PORTREVISION after e50c876e295af951485b605b8cb9bf567b6c23e1

I should have done it as part of the update.

Reported by: Tomoaki Aoki <junchoon_dec.sakura.ne.jp>

(cherry picked from commit 5939c6e5b2e0fdbf67f1238d2bf3a52dd01dbc89)