opp: Don't drop reference for an OPP table that was never parsed

dev_pm_opp_remove_table() should drop a reference to the OPP table only
if the DT OPP table was parsed earlier with a call to
dev_pm_opp_of_add_table() earlier. Else it may end up dropping the
reference to the OPP table, which was added as a result of other calls
like dev_pm_opp_set_clkname(). And would hence result in undesirable
behavior later on when caller would try to free the resource again.

Fixes: 03758d60

 ("opp: Replace list_kref with a local counter")
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>