drm/amd/display: Remove the unused function dmub_outbox_irq_info_funcs

The function dmub_outbox_irq_info_funcs is defined in the
irq_service_dcn201.c file, but not called elsewhere, so remove this
unused function.

drivers/gpu/drm/amd/amdgpu/../display/dc/irq/dcn201/irq_service_dcn201.c:139:43: warning: unused variable 'dmub_outbox_irq_info_funcs'.

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=3520


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>