ARM: ux500: Remove platform registration of MSP devices

This patch removes platform device registration of all 4 MSP
devices. It also takes care of all redundant infrastructure now
that each of the ux500 audio components have been Device Tree
enabled.

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