src: Add missing 'void' in function definition

Change-Id: I7fa1f9402b177a036f08bf99c98a6191c35fa0b5
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61371
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jason Glenesk <jason.glenesk@gmail.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/southbridge/amd/cimx/sb800/spi.c

@@ -32,7 +32,7 @@ static void execute_command(void)
 	       (read8((void *)(spibar+3)) & 0x80));
 }
 
-void spi_init()
+void spi_init(void)
 {
 	struct device *dev;