Since commit 7c41cdcd ("OPP: Simplify the over-designed pstate <->
level dance"), there is no longer any need for genpd providers to assign
the ->opp_to_performance_state(), hence let's drop it.

Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>
Cc: linux-arm-msm@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20231012153550.101425-1-ulf.hansson@linaro.org