arm64: dts: qcom: sa8775p: add the i2c18 node

Add a disabled node for the I2C interface that's exposed on the
sa8775p-ride development board.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230309103752.173541-4-brgl@bgdev.pl