ARM: shmobile: r8a7779: remove DIV4 clocks and use fixed ratio clock

R-Car H1 has many clocks, and it is possible to read/use clock ratio
of these clocks from FRQMRx as DIV4 clocks.
But, these ratio are fixed value and these are decided
by MD pin status.
This means that we can use fixed ratio clock via MD pin status,
instead of DIV4 clocks.

This patch reads MD pin status, and sets PLLA clock (= root clock),
and used fixed ratio clock for other clocks.
It was tesed on marzen board.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>