opp: Add apis to retrieve opps with interconnect bandwidth

Add dev_pm_opp_find_bw_ceil and dev_pm_opp_find_bw_floor to retrieve opps
based on interconnect associated with the opp and bandwidth. The index
variable is the index of the interconnect as specified in the opp table
in Devicetree.

Co-developed-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>