i2c: mv64xxx: enable the driver on ARCH_MVEBU

The new ARM64 Marvell Armada 7K/8K SoC family is using the same I2C
controller as the 32-bits Marvell EBU SoCs, so this commit allows
mv64xxx to be enabled when ARCH_MVEBU=y.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>