drm/amd/display: Remove duplicate 'update_idle_uclk' in dcn401 clk_mgr code

[WHY]
The coverity analysis flagged this if expression as it contains a
'CONSTANT_EXPRESSION_RESULT': 'update_idle_uclk' is 'ORd' with itself.

[HOW]
Removed the duplicate 'update_idle_uclk'.

Reviewed-by: Alex Hung <alex.hung@amd.com>
Acked-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Signed-off-by: Ivan Lipski <ivlipski@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>