arm64: dts: apq8016-sbc: move sdhci node under soc node

To be consistent with other nodes move sdhci node under the soc node,
rather than using lable references.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>