arm64: dts: mediatek: Add I2C support for MT6797 SoC

arm64: dts: mediatek: Add I2C support for MT6797 SoC

Add I2C support for Mediatek MT6797 SoC. There are a total of 8 I2C
controllers in this SoC (2 being shared) and they are same as the
controllers present in MT6577 SoC. Hence, the driver support is added with
DT fallback method.

As per the datasheet, there are controllers with _imm prefix like i2c2_imm
and i2c3_imm. These appears to be in different memory regions but sharing
the same pins with i2c2 and i2c3 respectively. Since there is no clear
evidence of what they really are, I've adapted the numbering/naming scheme
from the downstream code by Mediatek.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20200222162444.11590-3-manivannan.sadhasivam@linaro.org
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>