loader efifb: implement uga_autoresize as a call to text_autoresize

UGA does not have the same kind of mode enumeration that GOP does. Implement
it instead as a call to text_autoresize so that firmwares with only UGA
present still get some kind of autoresizing behavior.

While here, rename a typo'd "gop" to "uga", although it will remain unused
for the time being.