spi: omap2-mcspi: Add gpio_request and init CS

If GPIO chip select is specified, request the GPIO in the setup function
and release it in the cleanup function.

Signed-off-by: Michael Welling <mwelling@ieee.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --cc drivers/spi/spi-omap2-mcspi.c
Simple merge