arm64: dts: qcom: sa8775p: add the spi16 node

Add the SPI controller node for the interface exposed on the sa8775p-ride
development board.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230309103752.173541-6-brgl@bgdev.pl