dsp: add bootloader

It works!!

dsp/hello.c

@@ -0,0 +1,35 @@
+#include "sys.h"
+
+#define CYCLES_PER_MS 6666  // ish
+
+void busy_sleep_1ms() {
+  for (int i = 0; i < CYCLES_PER_MS; ++i) {
+    // nothing
+  }
+}
+
+/** waits a general amount of time */
+void busy_sleep(int ms) {
+  for (int i = 0; i < ms; ++i) {
+    busy_sleep_1ms();
+  }
+}
+
+int strlen(const char* str) {
+  int i = 0;
+  while(str[i] != '\0') {
+    i++;
+  }
+  return i;
+}
+
+void log(const char* stuff) {
+  uart_writen(uart0, stuff, strlen(stuff));
+}
+
+int main() {
+  while(1) {
+    log("Hello, world!\r\n");
+    busy_sleep(1000);
+  }
+}