At the moment we have two I2C stub drivers (for the Allwinner and the
Marvell platform), which #include the actual .c driver file.
Change this into the more usual design, by renaming and moving the stub
drivers into platform specific header files and including these from the
actual driver file. The platform specific include directories make sure
the driver picks up the right header automatically.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>

The I2C controller on Allwinner SoCs after A31 has a inverted interrupt
clear flag, which needs to be written 1 (rather than 0 on Marvell SoCs
and old Allwinner SoCs) to clear.

Add such a quirk to mi2cv driver common code.

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

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>