move boot_storage.h/.c to bdk/storage, check result of ensure_partition

bdk/storage/boot_storage.h

@@ -0,0 +1,16 @@
+#ifndef _BOOT_STORAGE_H
+#define _BOOT_STORAGE_H
+
+#include <utils/types.h>
+
+// check if boot1 (1mb), boot1, gpp, sd (in that order) have fat32 partition,
+// mount the partition and set the current drive to it
+bool boot_storage_mount();
+
+void boot_storage_unmount();
+void boot_storage_end();
+
+bool boot_storage_get_mounted();
+bool boot_storage_get_initialized();
+
+#endif