sfc: Fix type of FALCON_SPI_MAX_LEN

FALCON_SPI_MAX_LEN has type size_t while other SPI lengths have type
unsigned int.  This results in warnings from min() on 64-bit
architectures where they are different.  Add a cast to make it match.

From: Steve Hodgson <shodgson@solarflare.com>
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/net/sfc/falcon.c b/drivers/net/sfc/falcon.c
index d30c938..31ed1f4 100644
--- a/drivers/net/sfc/falcon.c
+++ b/drivers/net/sfc/falcon.c
@@ -1605,7 +1605,7 @@
  **************************************************************************
  */
 
-#define FALCON_SPI_MAX_LEN sizeof(efx_oword_t)
+#define FALCON_SPI_MAX_LEN ((unsigned) sizeof(efx_oword_t))
 
 /* Wait for SPI command completion */
 static int falcon_spi_wait(struct efx_nic *efx)