ARM: shmobile: r8a7779: Remove legacy SoC code

Now when the Marzen legacy board code is gone this patch
removes the unused r8a7779 legacy SoC code.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>