spi: Add export.h for THIS_MODULE/EXPORT_SYMBOL to spi.c

This uses both EXPORT_SYMBOL and THIS_MODULE, both which come from
the export.h file now.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

drivers/spi/spi.c

@@ -29,6 +29,7 @@
 #include <linux/spi/spi.h>
 #include <linux/of_spi.h>
 #include <linux/pm_runtime.h>
+#include <linux/export.h>
 
 static void spidev_release(struct device *dev)
 {