drm/amdgpu/pm/smu11: Fix fan set speed bug

Fix fan set speed calculation.

Suggested-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org