apq8016-sbc.dtsi is the only remaining device which takes up
4 files since it has its pinctrl split into separate files.

Actually this does not really make the device tree easier to read
(just harder to find nodes). For db820c the files were merged in
commit 88264f1f ("arm64: dts: qcom: db820c: Remove pin specific files").

Do the same for apq8016-sbc (db410c) and move the pinctrl definitions
into apq8016-sbc.dtsi.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20200514112754.148919-3-stephan@gerhold.netSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>