graphics/drm-fbsd12.0-kmod: Update snapshot

Update snapshot of graphics/drm-fbsd12.0-kmod to include a fix for a memory
leak.

FreeBSD Graphics issue: #155

			https://github.com/FreeBSDDesktop/kms-drm/issues/155

PR: 238925
Reported by: Ting-Wei Lan
MFH: 2019Q3 (implicit, drm-drivers blanket)
Sponsored by: B3 Init (zeising)