In preparation for adding the Sony Xperia Z3 smartphone, split the
common parts into shinano-common.dtsi.

No functional change intended.
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Link: https://lore.kernel.org/r/20240314-shinano-common-v2-1-a0fce1c72c74@z3ntu.xyzSigned-off-by: Bjorn Andersson <andersson@kernel.org>