fs: return device filesystem is mounted on

kernel-src/include/kernel/tmpfs.h

@@ -9,6 +9,7 @@
 typedef struct tmpfs_t {
 	vfs_t vfs;
 	uintmax_t inodenumber;
+	uintmax_t id;
 } tmpfs_t;
 
 typedef struct tmpfsnode_t {

kernel-src/include/kernel/vfs.h

@@ -38,6 +38,8 @@ typedef struct {
 	timespec_t ctime;
 	int rdevmajor;
 	int rdevminor;
+	int devmajor;
+	int devminor;
 	size_t blocksused;
 } vattr_t;