efi/console: Fix the "enter" key not working on x86 tablets

efi/console: Fix the "enter" key not working on x86 tablets

Most 8" or 7" x86 Windows 10 tablets come with volume up/down buttons and
a power-button. In their UEFI these are almost always mapped to arrow
up/down and enter.

Pressing the volume buttons (sometimes by accident) will stop the
menu countdown, but the power-button / "enter" key was not being recognized
as enter, so the user would be stuck at the grub menu.

The problem is that these tablets send scan_code 13 or 0x0d for the
power-button, which officialy maps to the F3 key. They also set
unicode_char to 0x0d.

This commit recognizes the special case of both scan_code and unicode_char
being set to 0x0d and treats this as an enter key press.

This fixes things getting stuck at the grub-menu and allows the user
to choice a grub-menu entry using the buttons on the tablet.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>