cpufreq: ti-cpufreq: Fix an incorrect error return value

Commit 05829d94 (cpufreq: ti-cpufreq: kfree opp_data when
failure) has fixed a memory leak in the failure path, however
the patch returned a positive value on get_cpu_device() failure
instead of the previous negative value. Fix this incorrect error
return value properly.

Fixes: 05829d94 (cpufreq: ti-cpufreq: kfree opp_data when failure)
Cc: 4.14+ <stable@vger.kernel.org> # v4.14+
Signed-off-by: Suman Anna <s-anna@ti.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>