h8300: remove unnecessary of_platform_populate call

The DT core will call of_platform_populate, so it is not necessary for
arch specific code to call it unless there are custom match entries,
auxdata or parent device. Neither of those apply here, so remove the call.

Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: uclinux-h8-devel@lists.sourceforge.jp
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Yoshinori Sato <ysato@users.sourceforge.jp>