venus: pm_helpers: Set opp clock name for v1

The rate of the core clock is set through devm_pm_opp_set_rate and
to avoid errors from it we have to set the name of the clock via
dev_pm_opp_set_clkname.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Aníbal Limón <anibal.limon@linaro.org>