Reorganize and fix problems (returns) in the bootm command.

Do *NOT* return after the "point of no return" has been passed.
  If something goes wrong, the board must be reset after that point.
Move the "Transferring control to Linux" debug message back to where it
  belongs: just before transferring control to linux.

Signed-off-by: Gerald Van Baren <vanbaren@cideas.com>