greybus: es{1,2}: remove obselete define

The SVC Control request is obsolete and not used anymore. Remove the related
define.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>