ARM: dts: orion5x-lschl: More consistent naming on linkstation series

DTS files, which includes orion5x-linkstation.dtsi, are named:
  orion5x-linkstation-*.dts

So we rename the file below:
  arch/arm/boot/dts/orion5x-lschl.dts
to the new name:
  arch/arm/boot/dts/orion5x-linkstation-lschl.dts

Because DTS conversion of this device was just introduced in 4.9, Debian
is still using legacy device support, other distros are the same,
so here we won't expect any impact actually.

Fixes: f94f2689

 ("ARM: dts: orion5x: convert ls-chl to FDT")
Cc: Ashley Hughes <ashley.hughes@blueyonder.co.uk>
Signed-off-by: Roger Shimizu <rogershimizu@gmail.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>