fbdev: sh_mipi_dsi: add HSxxCLK support

SH MIPI manual explains the calculation method of HBP/HFP.
it is based on HSbyteCLK settings.
SH73a0 chip can use HS6divCLK/HS4divCLK for it.
This patch has compatibility to SH7372 mipi

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>