drivers: mentor: extract MI2CV driver from Marvell driver

The Marvell A8K SoCs use the MI2CV IP core from Mentor Graphics, which
is also used by Allwinner.

As Mentor Graphics allows a lot of customization, the MI2CV in the two
SoC families are not compatible, and driver modifications are needed.

Extract the common code to a MI2CV driver.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>