ARM: shmobile: r8a7779: Generic CCF and timer support

Add a r8a7779-specific callback to initialize CCF and
clocksources. With this in place we are one step closer
to be able to use r8a7779 without C board code.

Also add a multiplatform wrapper to avoid breaking the
r8a7779 marzen legacy case.

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>