mx31ads: Configure SSI5 pins in IOMUX for PMIC module audio support

SSI5 on the CPU is connected to the PMIC module to provide audio support
so unconditionally configure the relevant pins on the CPU to route out
the signals.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>