ARM: OMAP: board-am3517evm: Configure McBSP1 CLKR/FSR signal source

am3517evm board uses McBSP1 for audio with 4pin configuration.
The CLKR/FSR signals need to be connected to CLKX/FSX pin of the SoC in
this case.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>