ARM: dts: Cygnus: Drop incorrect io-channel-ranges property.

This property applies to consumers of io-channels.  In this case we
have a provider so the property is not used.

Recent changes to dt-schema result int his being reported as an error
as a dependency is enforced between this property and io-channels.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>