staging: board: kzm9d: Board staging support for emxx_udc

Add staging board support for the KZM9D board and add
an emxx_udc platform device to allow in-tree continous
development of the driver on the KZM9D board.

When DT bindings are ready for the emxx_udc driver then
the platform device in the KZM9D staging board code can
easily be removed. Until then we use platform devices
to continously improve the driver and integration code.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>