davinci: da850: move da850_evm specific mcasp pins to board file.

The da850_mcasp_pins pinmux array is specific to the da850_evm, and is
not generic.  Move the array to the board file, make it static initdata,
and rename it accordingly.

Signed-off-by: Michael Williamson <michael.williamson@criticallink.com>
Tested-by: Sudhakar Rajashekhara <sudhakar.raj@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>