ARM: kirkwood: remove lagacy clk workarounds

With legacy devices converted to DT and a proper ethernet MAC
workaround, we can now remove the clk workarounds for legacy
devices. While at it, also cleanup the list of includes.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>