cfg: remove unnecessary check for jump type

This condition should match any jump with two successors. This is
needed on riscv64, where there is no flags register, so Jjnz is
used all the way to emit().

cfg.c

@@ -298,7 +298,6 @@ simpljmp(Fn *fn)
 
 	Blk **uf; /* union-find */
 	Blk **p, *b, *ret;
-	int c;
 
 	ret = blknew();
 	ret->id = fn->nblk++;
@@ -322,9 +321,7 @@ simpljmp(Fn *fn)
 			uffind(&b->s1, uf);
 		if (b->s2)
 			uffind(&b->s2, uf);
-		c = b->jmp.type - Jjf;
-		if (0 <= c && c <= NCmp)
-		if (b->s1 == b->s2) {
+		if (b->s1 && b->s1 == b->s2) {
 			b->jmp.type = Jjmp;
 			b->s2 = 0;
 		}