drm/amd/display: remove duplicate include in dcn201_clk_mgr.c

Remove all but the first include of reg_helper.h and core_types.h
from dcn201_clk_mgr.c.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Lv Ruyi <lv.ruyi@zte.com.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>