ARM: shmobile: r8a7778: Common clock framework DT description

Declares all r8a7778 clocks supported by the legacy clock framework,
plus tmu2.

Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
[horms: only included dtsi changes]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>