UPSTREAM: OPP: Add support for parsing the 'opp-level' property

Now that the OPP bindings are updated to include an optional
'opp-level' property, add support to parse it from device tree
and store it as part of dev_pm_opp structure.
Also add and export an helper 'dev_pm_opp_get_level()' that can be
used to get the level value read from device tree when present.

Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>
(cherry picked from commit 5b93ac54
https://github.com/torvalds/linux.git

)
Signed-off-by: Niklas Cassel <niklas.cassel@linaro.org>

BUG=b:129558664
TEST=Validate DVFS and schedutil governor
Git-repo: https://git.linaro.org/people/niklas.cassel/kernel.git


Git-commit: 1a9bfc857188d08b02eece73cc7cbb66c6c4741e
Signed-off-by: Praveen Koya <pkoya@codeaurora.org>

Change-Id: I7f67d17cdff42a7aa69d855ac52a7ee4e24f8403
Signed-off-by: Vamsi Singamsetty <vamssi@codeaurora.org>
Signed-off-by: Khasim Syed Mohammed <khasim.mohammed@linaro.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/1664359


Reviewed-by: Zhihong Yu <zhihongyu@chromium.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Commit-Queue: Zhihong Yu <zhihongyu@chromium.org>
Tested-by: Zhihong Yu <zhihongyu@chromium.org>