spi: Add module.h to implicit users in drivers/spi

We are clipping down the presence of module.h, since it was
everywhere.  If you really need it, you better call it out,
as per this changeset.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/spi/spi-bitbang.c b/drivers/spi/spi-bitbang.c
index 02d57fb..aef59b1 100644
--- a/drivers/spi/spi-bitbang.c
+++ b/drivers/spi/spi-bitbang.c
@@ -20,6 +20,7 @@
 #include <linux/spinlock.h>
 #include <linux/workqueue.h>
 #include <linux/interrupt.h>
+#include <linux/module.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
 #include <linux/platform_device.h>