drm/amd/amdgpu: Allow broadcast on debugfs read (v2)

Allow any of the se/sh/instance fields to be
specified as a broadcast by submitting 0x3FF.

(v2) Fix broadcast range checking

Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>