Version 4.2.4 of gcc produces the following warnings without this change:
  mkimage.c: In function ‘main’:
  mkimage.c:204: warning: dereferencing type-punned pointer will break strict-aliasing rules
  mkimage.c:222: warning: dereferencing type-punned pointer will break strict-aliasing rules

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>