i2c: rcar: rework hw init

i2c: rcar: rework hw init

commit 2c78cdc1c06308a59d6ed4145cdba73fdeff8c0d upstream.

We don't need to init HW before every transfer since we know the HW
state then. HW init at probe time is enough. While here, add setting the
clock register which belongs to init HW. Also, set MDBS bit since not
setting it is prohibited according to the manual.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Chris Paterson <Chris.Paterson2@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>