ARM: zynq: Remove skeleton.dtsi

Based on
"ARM: dts: explicitly mark skeleton.dtsi as deprecated"
(sha1: 9c0da3cc

)
skeleton.dtsi is deprecated.
Move address and size-cells directly to zynq-7000.dtsi.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Julia Cartwright <julia@ni.com>