boot1 EFI: reset the screen and select the best mode.

boot1 EFI: reset the screen and select the best mode.

It's necessary to reset the screen to make sure any vendor pixels are
gone when we start boot1.  In the Lenovo X1 (3rd gen), this is the
only way to clear the screen.  Previously, the Lenovo logo would only
disappear after the kernel started scrolling the display.

After resetting the screen, EFI could put us in the worst LCD mode
(oversized characters), so we now find the largest mode we can use and
hope it's the most appropriate one (it's not trivial to tell what's
the correct LCD resolution at this point).  It's worth noting that the
final stage loader has a 'mode' command that can be used to switch
text modes.

While there, enable the software cursor, just like in the legacy boot
mode.

MFC after:	1 week