ARM: ux500: Add support for MSP I2S-devices

Create devices for the MSP-blocks (MSP0, MSP1, MSP2 and MSP3)
and associate it with the correct clocks in the clock-framework.

Signed-off-by: Ola Lilja <ola.o.lilja@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>