spi/devicetree: Move devicetree support code into spi directory

The SPI device tree support code isn't shared by any other subsystem.  It can
be moved into the core drivers/spi directory and the exported symbol can be
removed.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Rob Herring <rob.herring@calxeda.com>

drivers/spi/spi-fsl-espi.c

@@ -17,7 +17,6 @@
 #include <linux/mm.h>
 #include <linux/of.h>
 #include <linux/of_platform.h>
-#include <linux/of_spi.h>
 #include <linux/interrupt.h>
 #include <linux/err.h>
 #include <sysdev/fsl_soc.h>