PM / OPP: fix debug/error messages in dev_pm_opp_of_get_sharing_cpus()

These log messages are wrong because _of_get_opp_desc_node() returns
an operating-points-v2 node.

Commit a6eed752 ("PM / OPP: passing NULL to PTR_ERR()") fixed
static checker warnings, and reworded the messages at the same time
(but the latter was not mentioned in the git-log).

Restore the correct messages.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>