drm/amd/powerplay: Don't return an error if fan table is missing

BugLink: http://bugs.launchpad.net/bugs/1546572

It's a valid configuration on some laptops.
Reviewed-by: Tom St Denis <tom.stdenis@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 283b1a8b)
Signed-off-by: Alberto Milone <alberto.milone@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/gpu/drm/amd/powerplay/hwmgr/tonga_processpptables.c

@@ -797,7 +797,7 @@ static int init_thermal_controller(
 		  );
 
 	if (0 == powerplay_table->usFanTableOffset)
-		return -1;
+		return 0;
 
 	fan_table = (const PPTable_Generic_SubTable_Header *)
 		(((unsigned long)powerplay_table) +