Add simple NVMe module and switch to NVMe emulation

src/kernel/nvme.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include <stdint.h>
+
+void nvme_init(); // Assuming one and only one NVMe device.
+
+void nvme_read_sectors(uint32_t index, uint8_t count, void *to);
+
+void nvme_write_sectors(uint32_t index, uint8_t count, const void *from);