i2c: mvtwsi: Support for up to 4 different controllers

i2c: mvtwsi: Support for up to 4 different controllers

Orion5x, Kirkwood and Armada XP platforms come with a single TWSI (I2C) MVTWSI
controller. However, other platforms using MVTWSI may come with more: this is
the case on Allwinner (sunxi) platforms, where up to 4 controllers can be found
on the same chip.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Acked-by: Heiko Schocher <hs@denx.de>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>