MFC r348059: vt efifb: add suspend/resume calls

Using the latest NVIDIA driver, upon resuming from suspend with X
running the display remained blank. Additionally OpenGL applications
that were running triggered a number of error messages from the NVIDIA
driver.

This occurred because the vt efifb back-end did not signal the X server
to release the display before suspending (or to re-acquire it after
resuming). The NVIDIA driver includes code for smoothly shutting down
and re-initializing the GPU, which was not getting called.

Since the NVIDIA driver doesn't currently support framebuffer devices
and vt is forced to fall back to the efifb back-end, add vd_suspend and
vd_resume members to connect the suspend/resume path. This ensures the
X server is properly able to re-initialize the display.

PR: 237050
Submitted by: Erik Kurzinger <ekurzinger@nvidia.com>