arm: qemu: Enable usb keyboard as an input device

Commit 02be57ca ("riscv: qemu: Enable usb keyboard as an input
device") adds PCI xHCI support to QEMU RISC-V virtual machines and
enables using a USB keyboard as one of the input devices. Similarly,
enable those for ARM virtual machines as well.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng@tinylab.org>