efi_console: Stay inline with the UEFI spec

The UEFI spec states that the minimum garunteed terminal resolution is
80x25.

Signed-off-by: Ahmad Khalifa <ahmadkhalifa570@gmail.com>
Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/1292
(cherry picked from commit 3b68c491d37196bb76a95bce3c02f7c6d5ba22fd)