drm/amd/display: Remove duplicated include in dcn35_hwseq.c

./drivers/gpu/drm/amd/display/dc/dcn35/dcn35_hwseq.c: clk_mgr.h is included more than once.

Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>