drm/amd/pm/swsmu/smu13/smu_v13_0: Prevent division by zero

drm/amd/pm/swsmu/smu13/smu_v13_0: Prevent division by zero

commit f23e9116ebb71b63fe9cec0dcac792aa9af30b0c upstream.

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: c05d1c401572 ("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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>