Add the Denali disk driver.

Begin enumerating information from the PCI structure and HBA AHCI
structures.

Currently the PCI structure address is hardcoded but it should be
passed via a capability from the init process in the future.

sys/denali/denali.cpp

@@ -0,0 +1,8 @@
+#include <stdint.h>
+
+#include "ahci/ahci_driver.h"
+
+int main(uint64_t bootstrap_cap) {
+  AhciDriver driver;
+  return driver.Init();
+}