graphics/drm-next-kmod: update to later github snapshot which includes improvements made in response to bug reports and removes the collision of the port's drm.ko with base drm.ko. Also increase the FreeBSD version check in response to PR 221937. Additionally, improve pkg-message and note that radeonkms is also available in this port.

PR: 221937
Reviewed by: swills (mentor)
Approved by: swills (mentor)
Differential Revision: https://reviews.freebsd.org/D12348