opp: Remove bandwidth votes when target_freq is zero

We already drop several votes when target_freq is set to zero, drop
bandwidth votes as well.

Reported-by: Sibi Sankar <sibis@codeaurora.org>
Reviewed-by: Georgi Djakov <georgi.djakov@linaro.org>
Tested-by: Georgi Djakov <georgi.djakov@linaro.org>
Reviewed-by: Sibi Sankar <sibis@codeaurora.org>
Tested-by: Sibi Sankar <sibis@codeaurora.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>