i2c: riic: Add support for fast mode plus

i2c: riic: Add support for fast mode plus

Fast mode plus is available on most of the IP variants that RIIC driver
is working with. The exception is (according to HW manuals of the SoCs
where this IP is available) the Renesas RZ/A1H. For this, patch
introduces the struct riic_of_data::fast_mode_plus.

Fast mode plus was tested on RZ/G3S, RZ/G2{L,UL,LC}, RZ/Five by
instantiating the RIIC frequency to 1MHz and issuing i2c reads on the
fast mode plus capable devices (and the i2c clock frequency was checked on
RZ/G3S).

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>