drm/amd/pm: Prevent division by zero

The user can set any speed value.
If speed is greater than UINT_MAX/8, division by zero is possible.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: c05d1c4 ("drm/amd/swsmu: add aldebaran smu13 ip support (v3)")
Signed-off-by: Denis Arefev <arefev@swemel.ru>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

Author: Denis Arefev

drivers/gpu/drm/amd/pm/swsmu/smu13/smu_v13_0.c

@@ -1226,7 +1226,7 @@ int smu_v13_0_set_fan_speed_rpm(struct smu_context *smu,
 	uint32_t tach_period;
 	int ret;
 
-	if (!speed)
+	if (!speed || speed > UINT_MAX/8)
 		return -EINVAL;
 
 	ret = smu_v13_0_auto_fan_control(smu, 0);