Hardcoding the maximum numbers could result in spurious error messages
from the IRQ state callbacks, e.g. on Polaris 11/12:

[drm:dce_v11_0_set_pageflip_irq_state [amdgpu]] *ERROR* invalid pageflip crtc 5
[drm:amdgpu_irq_disable_all [amdgpu]] *ERROR* error disabling interrupt (-22)
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>