sfc: Change SPI lengths to type size_t

Based on a patch by Andrew Morton.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/sfc/spi.h b/drivers/net/sfc/spi.h
index c4aca13..38e22ff 100644
--- a/drivers/net/sfc/spi.h
+++ b/drivers/net/sfc/spi.h
@@ -68,7 +68,7 @@
 };
 
 int falcon_spi_cmd(const struct efx_spi_device *spi, unsigned int command,
-		   int address, const void* in, void *out, unsigned int len);
+		   int address, const void* in, void *out, size_t len);
 int falcon_spi_fast_wait(const struct efx_spi_device *spi);
 int falcon_spi_read(const struct efx_spi_device *spi, loff_t start,
 		    size_t len, size_t *retlen, u8 *buffer);