spi/omap2: mark omap2_mcspi_master_setup as __devinit

This warning recently appeared with omap2plus_defconfig:

WARNING: drivers/spi/built-in.o(.devinit.text+0x3c4): Section mismatch in reference from the function omap2_mcspi_probe() to the function .init.text:omap2_mcspi_master_setup()
The function __devinit omap2_mcspi_probe() references
a function __init omap2_mcspi_master_setup().
If omap2_mcspi_master_setup is only used by omap2_mcspi_probe then
annotate omap2_mcspi_master_setup with a matching annotation.

The fix is obviously to mark the omap2_mcspi_master_setup function as
__devinit, rather than __init.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>