staging: wilc1000: fix warning while printing

size_t should print using %zu, but here it was use %lu.
we were getting warning while printing.
Signed-off-by: Chris Park <chris.park@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wilc1000/wilc_spi.c

@@ -404,7 +404,7 @@ static int spi_cmd_complete(uint8_t cmd, uint32_t adr, uint8_t *b, uint32_t sz,
 #undef NUM_DUMMY_BYTES
 
 	if (len2 > (sizeof(wb) / sizeof(wb[0]))) {
-		PRINT_ER("[wilc spi]: spi buffer size too small (%d) (%lu)\n",
+		PRINT_ER("[wilc spi]: spi buffer size too small (%d) (%zu)\n",
 			 len2, (sizeof(wb) / sizeof(wb[0])));
 		result = N_FAIL;
 		return result;