arm64: dts: qcom: c630: Move panel to aux-bus

With the newly introduced aux-bus under the TI SN65DSI86 the panel
node should be described as a child instead of a standalone node, move
it there.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Tested-by: Steev Klimaszewski <steev@kali.org>
Link: https://lore.kernel.org/r/20220208041606.144039-2-bjorn.andersson@linaro.org