mach-ux500: remove most of the ugly machine_is_*() calls

Do more work in the per-machine init calls instead of customizing
each init call.

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