mtd: denali: fix include guard and license block of denali.h

It looks like this header file is a concatenation of two headers.
Anyway, the include guard should be renamed and placed at the correct
postion and the license block in the middle should be deleted.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>