ARM: dts: cros-ec-keyboard: Use keymap macros

The common cros-ec keymap has been defined as macros. This patch uses
the macros to simply linux,keymap in cros-ec-keyboard.dtsi file.

This patch also creates an alias for keyboard-controller to make it
easier to override the keymap in board-specific dts later.

Signed-off-by: Philip Chen <philipchen@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20210115143555.v6.2.I9ec9c3c61eded22a5f7fbff838d23fc95ec7cfe0@changeid


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>