opp: core: Fix off by one in dev_pm_opp_get_bw()

The "opp->bandwidth" array has "opp->opp_table->path_count" number of
elements.  It's allocated in _opp_allocate().  So this > needs to be >=
to prevent an out of bounds access.

Fixes: d78653dcd8bf ("opp: core: implement dev_pm_opp_get_bw")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>