ARM: ux500: build ccu8540 device tree blob

This makes sure the new ccu8540 DTB file is generated by
the build system.

Cc: Lee Jones <lee.jones@linaro.org>
Cc: Gabriel Fernandez <gabriel.fernandez.st@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>