drm/amd/display: Remove redundant includes from DC

drm/amd/display: Remove redundant includes from DC

[Why]
The explicit include of linux/array_size.h in Display Core (DC) is
redundant. The ARRAY_SIZE macro is already provided by dm_services.h
(via os_types.h) which DC includes.

[How]
Remove the unnecessary #include <linux/array_size.h> from
dc_hw_sequencer.c and dce_clock_source.c.

Fixes: 2d2366176445 ("drm/amd/display: Replace inline NUM_ELEMENTS macro with ARRAY_SIZE")
CC: Linus Probert <linus.probert@gmail.com>
Signed-off-by: Roman Li <Roman.Li@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>