Add the ability to configure the MFP1->MFP5 registers
as GPIOs.  In addition adding ALSA controls to get and set
the GPIO state.

Per the data sheet each MFP can be configured as a GPIO
input only, output only or either an input or output.
Signed-off-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>