cpuidle: governor: Add new governors to cpuidle_governors again

commit 22782b3f9bb8ae21c710e2880db21bc729771e92 upstream

After commit 61cb5758d3c4 ("cpuidle: Add cpuidle.governor= command
line parameter") new cpuidle governors are not added to the list
of available governors, so governor selection via sysfs doesn't
work as expected (even though it is rarely used anyway).

Fix that by making cpuidle_register_governor() add new governors to
cpuidle_governors again.

Fixes: 61cb5758d3c4 ("cpuidle: Add cpuidle.governor= command line parameter")
Reported-by: NKees Cook <keescook@chromium.org>
Cc: 5.0+ <stable@vger.kernel.org> # 5.0+
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: NMichael Wang <yun.wang@linux.alibaba.com>

drivers/cpuidle/governor.c

@@ -90,6 +90,7 @@ int cpuidle_register_governor(struct cpuidle_governor *gov)
 	mutex_lock(&cpuidle_lock);
 	if (cpuidle_find_governor(gov->name) == NULL) {
 		ret = 0;
+		list_add_tail(&gov->governor_list, &cpuidle_governors);
 		if (!cpuidle_curr_governor ||
 		    !strncasecmp(param_governor, gov->name, CPUIDLE_NAME_LEN) ||
 		    (cpuidle_curr_governor->rating < gov->rating &&