cpufreq: qoriq: allow building as module with THERMAL=m

My previous patch to avoid link errors with the qoriq cpufreq
driver disallowed all of the broken cases, but also prevented
the driver from being built when CONFIG_THERMAL is a module.

This changes the dependency to allow the cpufreq driver to
also be a module in this case, just not built-in.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 8ae1702a (cpufreq: qoriq: Register cooling device based on device tree)
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>