MFC: r287299 [1]

Add a gop command to help diagnose VT efifb problems. The gop
command has the following sub-commands:
list - list all possible modes (paged)
get - return the current mode
set <mode> - set the current mode to <mode>

MFC: r287317, r287422, r287475, r287489, r287538 [2]

Add support for the UGA draw protocol. This includes adding a
command called 'uga' to show whether UGA is implemented by the
firmware and what the settings are. It also includes filling
the efi_fb structure from the UGA information when GOP isn't
implemented by the firmware.

PR: 207313 [1], 202730 [2]
Approved by: re (gjb)