ARM: rmobile: Update H2 Stout

The H2 Stout port was broken since some time. This patch updates
the H2 Stout port to use modern frameworks, DM, DT probing, SPL
and TPL for the preloading and puts it on par with the M2 Porter
board.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>