strcmp: Remove unnecessary check for *r

If *l == *r && *l, then by transitivity, *r.

src/string/strcmp.c

@@ -2,6 +2,6 @@
 
 int strcmp(const char *l, const char *r)
 {
-	for (; *l==*r && *l && *r; l++, r++);
+	for (; *l==*r && *l; l++, r++);
 	return *(unsigned char *)l - *(unsigned char *)r;
 }