fix comment in mkfs.c

mkfs/mkfs.c

@@ -42,7 +42,7 @@ uint ialloc(ushort type);
 void iappend(uint inum, void *p, int n);
 void die(const char *);
 
-// convert to intel byte order
+// convert to riscv byte order
 ushort
 xshort(ushort x)
 {