drm/amd/display: Fix divide by zero when calculating min ODM factor

[WHY&HOW]
If the debug option is set to disable_dsc the max slice width and/or
dispclk can be zero. This causes a divide by zero when calculating the
min ODM combine factor. Add a check to ensure they are valid first.

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org