drivers/pc80/rtc/mc146818rtc_boot: Use size_t for length

Change-Id: I877e19c014759e33b9cc48ff9ee27e898737aece
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33805
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/drivers/pc80/rtc/mc146818rtc_boot.c

@@ -67,7 +67,7 @@ void sanitize_cmos(void)
 					CBFS_COMPONENT_CMOS_DEFAULT, &length);
 #endif
 		if (cmos_default) {
-			int i;
+			size_t i;
 			cmos_disable_rtc();
 			for (i = 14; i < MIN(128, length); i++)
 				cmos_write_inner(cmos_default[i], i);