drm/amd/display: Remove redundant condition with DEADCODE

[WHY]
Coverity analysis flagged this condition as DEADCODE since the
variable 'req128_c' is always false, thus the condition is never
true.

[HOW]
Remove the condition.

Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Ivan Lipski <ivlipski@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>