arm64: dts: qcom: sc7280: add IPA information

Add IPA-related nodes and definitions to "sc7280.dtsi", including
the reserved memory area used for AP-based IPA firmware loading.

Signed-off-by: Alex Elder <elder@linaro.org>
Link: https://lore.kernel.org/r/20210804210214.1891755-2-elder@linaro.org


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>