dm: input: Create a keyboard uclass

Add a uclass for keyboard input, mirroring the existing stdio methods.
This is enabled by a new CONFIG_DM_KEYBOARD option.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
5 files changed