graphics/gpu-firmware-kmod: Add more firmware files (in particular for AMD's Raven Ridge and some of Intel's Skylake etc). This does not yet imply support for, e.g., Raven as that will require an update to the drm-next-kmod component.

Reviewed by: swills (mentor)
Approved by: swills (mentor)
Obtained from: FreeBSDDesktop (Intel additions by Johannes Lundberg)
Differential Revision: https://reviews.freebsd.org/D14277