Big code refactor, get rid of HAL entirely

kernel/rbuf/rbuf.c

@@ -1,9 +1,8 @@
 #include <stdint.h>
 #include <stddef.h>
 #include <stdbool.h>
-#include "rbuf.h"
+#include "rbuf/rbuf.h"
 #include "kprintf.h"
-#include "hal/hal.h"
 
 void rbuf_init(RBuf *rbuf, uint8_t *buf, size_t bufsize) {
   rbuf->buffer = buf;