sun50i: a64: A64-Teres-I board detect builtin keyboard

A64-Teres-I board is a laptop which comes with a builtin keyboard.
The keyboard+trackpad controller pauses for 2 seconds at a firmware
prompt before loading its HID interface.

U-Boot needs to wait equally long to reliably enable the keyboard.

Signed-off-by: Jonas Smedegaard <dr@jones.dk>
Reviewed-by: Tom Rini <trini@konsulko.com>
Series-Cc: Jagan Teki <jagan@amarulasolutions.com>
Series-Cc: Lukasz Majewski <lukma@denx.de>
Series-Cc: Andre Przywara <andre.przywara@arm.com>