config: Enable USB Keyboard support on RPi4

Supporting USB keyboards out of the box is both handy for development
and production. Notably if u-boot is used to boot into GRUB.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
[mb: drop rpi_4_32b_defconfig hunk]
Signed-off-by: Matthias Brugger <mbrugger@suse.com>