thermal: core: small style fix when checking for __find_governor()

Remove style issue:
CHECK: Comparison to NULL could be written "!__find_governor"
+	if (__find_governor(governor->name) == NULL) {

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>

drivers/thermal/thermal_core.c

@@ -136,7 +136,7 @@ int thermal_register_governor(struct thermal_governor *governor)
 	mutex_lock(&thermal_governor_lock);
 
 	err = -EBUSY;
-	if (__find_governor(governor->name) == NULL) {
+	if (!__find_governor(governor->name)) {
 		err = 0;
 		list_add(&governor->governor_list, &thermal_governor_list);
 		if (!def_governor && !strncmp(governor->name,
@@ -182,7 +182,7 @@ void thermal_unregister_governor(struct thermal_governor *governor)
 
 	mutex_lock(&thermal_governor_lock);
 
-	if (__find_governor(governor->name) == NULL)
+	if (!__find_governor(governor->name))
 		goto exit;
 
 	mutex_lock(&thermal_list_lock);