base-files: upgrade: fwtool.sh: rewording logs

The intent is to make it sound more like info level message, not some
error like "404 not found".  x86 target at the moment makes image with
only signature but no metadata (ref commit f8141216 "x86: append
metadata to combined images").

Signed-off-by: Yousong Zhou <[email protected]>
Reviewed-By: Philip Prindeville <[email protected]>

package/base-files/files/lib/upgrade/fwtool.sh

@@ -10,7 +10,7 @@ fwtool_check_signature() {
 	}
 
 	if ! fwtool -q -s /tmp/sysupgrade.ucert "$1"; then
-		v "Image signature not found"
+		v "Image signature not present"
 		[ "$REQUIRE_IMAGE_SIGNATURE" = 1 -a "$FORCE" != 1 ] && {
 			v "Use sysupgrade -F to override this check when downgrading or flashing to vendor firmware"
 		}
@@ -30,7 +30,7 @@ fwtool_check_image() {
 	. /usr/share/libubox/jshn.sh
 
 	if ! fwtool -q -i /tmp/sysupgrade.meta "$1"; then
-		v "Image metadata not found"
+		v "Image metadata not present"
 		[ "$REQUIRE_IMAGE_METADATA" = 1 -a "$FORCE" != 1 ] && {
 			v "Use sysupgrade -F to override this check when downgrading or flashing to vendor firmware"
 		}