intel_edison_fab_c.c: Don't initiate SPI pins when initializing MRAA

intel_edison_fab_c.c: Don't initiate SPI pins when initializing MRAA

Calling mraa_intel_edison_misc_spi() is not really needed, because the
GPIO 10..13 pins will be configured correctly when the user actually
inits them as GPIO pins. When using these pins for GPIO,
mraa_setup_mux_mapped() and mraa_intel_edison_gpio_init_post() will do
all this work based on the pin map and pinmodes for the Edison Arduino
board.

On the contrary, this function would break any user of the SPI bus
that is already running.

Signed-off-by: Jonas Norling <jonas.norling@connode.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>