drm/amd/display: Fix duplicate included dce110_hw_sequencer.h

Clean up the following includecheck warning:

./drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c:
dce110_hw_sequencer.h is included more than once.

No functional change.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>