lib/ucs2_string.c: add MODULE_LICENSE()

lib/ucs2_string.c: add MODULE_LICENSE()

Fix missing MODULE_LICENSE() warning in lib/ucs2_string.c:

  WARNING: modpost: missing MODULE_LICENSE() in lib/ucs2_string.o
  see include/linux/module.h for more information

Link: http://lkml.kernel.org/r/b2505bb4-dcf5-fc46-443d-e47db1cb2f59@infradead.org
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>