sata, highbank: send extra clock cycles in SGPIO patterns

Some SGPIO PICs don't follow the standard very well and expect a certain
number of clock cycles or port frames in each SGPIO pattern. Add two
optional parameters in the DTB that can provide the number of extra
clock cycles to be sent before and after SGPIO pattern. Read those
parameters from the DTB and send the extra clock cycles.

Signed-off-by: Mark Langsdorf <mark.langsdorf@calxeda.com>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Tejun Heo <tj@kernel.org>