ARM: orion5x: remove legacy support of ls-chl

This patch removes the legacy support of ls-chl which is converted to the
device tree.

[gregory.clement@free-electrons.com: removal extracted from a wider patch]
Signed-off-by: Ashley Hughes <ashley.hughes@blueyonder.co.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>