drivers/loop: Add a loop character device that can be used to setup and teardown loop devices

TODO

@@ -439,7 +439,6 @@ o Kernel/Protected Build
 
                COMMAND  KERNEL INTERFACE(s)
                -------- ----------------------------------------------
-               losetup  losetup(), loteardown()
                mkfatfs  mkfatfs
                mkrd     ramdisk_register()
                ps       sched_foreach()
@@ -454,22 +453,6 @@ o Kernel/Protected Build
 
                  http://git.busybox.net/busybox/tree/util-linux/mkfs_vfat.c
 
-               Here is how the Busybox/Linux losetup works:
-
-               This is the busybox losetup():
-
-                 http://git.busybox.net/busybox/tree/util-linux/losetup.c .
-
-               You can see that it relies on query_loop(), set_loop(), and
-               del_loop() to do the really work.  query_loop() and friends
-               are here:
-
-                 http://git.busybox.net/busybox/tree/libbb/loop.c.
-
-               They each open a device and interface with it using ioctl calls.
-               That is probably how NuttX should do things as well.  But that
-               is pretty much a redesign.
-
   Status:      Open
   Priority:    Medium/High -- the kernel build configuration is not fully fielded
                yet.