[SeaBIOS] bug: boot menu items 10+ cannot be selected

[Ian Kelling]

The boot menu says option 10, but when you type 10, it selects #1 as
soon as you press 1. I think an easy fix would be that when there are at
least 10 items in the boot menu to print 01, 02, etc. and read 2
characters. I don't care about this being fixed, just figured I'd
report it.