greybus: arche-apb: platform data 'apb' is guaranteed to be valid

Platform data 'apb' is guaranteed to be valid in arche_apb_ctrl_remove()
and so no need to check it.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>