arm64: dts: qcom: sa8155p-adp: Remove unneeded rgmii_phy information

Using interrupts-extended already indicates what the interrupt-parent
is, so drop the explicit interrupt-parent.

The comment about this being the phy-intr is not helpful either, since
this is the only interrupt in the phy node.

Suggested-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Reviewed-by: Brian Masney <bmasney@redhat.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230501212446.2570364-4-ahalaney@redhat.com