ARM: dts: kirkwood: split lswvl dts to linkstation lsvl and lswvl

LS-WVL/VL are both kirkwood-6282 based NAS devices, which share
many MPP pins. However they are slightly different:
  - LS-WVL is 2-Bay NAS, and LS-VL is only 1-Bay.
  - There're two red LED indicator on LS-WVL to show when HDD fails,
    which is similar to LS-WXL, but there's no such on LS-VL.

So after the split, common part goes into .dtsi file:
  - kirkwood-linkstation-6282.dtsi
while all rest part goes into device specific .dts file:
  - kirkwood-linkstation-lsvl.dts
  - kirkwood-linkstation-lswvl.dts

Signed-off-by: Roger Shimizu <rogershimizu@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>