drm/amd/display: Compare clock state member to determine optimization.

[Why]
It seems always request passive flip on RN due to incorrect compare
clock state to determine optization.

[How]
Instead of calling memcmp, compare clock state member to determine the
condition.

Signed-off-by: Yongqiang Sun <yongqiang.sun@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>