ARM: ux500: remove intermediary add_platform_device* functions

These are no longer required since a 'parent' pointer is now
passed to each registering device.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>