drm/amdgpu: Add parsing SQ_EDC_INFO to SQ IH v3.

drm/amdgpu: Add parsing SQ_EDC_INFO to SQ IH v3.

Access to SQ_EDC_INFO requires selecting register instance and
hence mutex lock when accessing GRBM_GFX_INDEX for which a work
is schedueled from IH. But SQ interrupt can be raised on many instances
at once which means queuing work will usually succeed for the first one
but fail for the rest since the work takes time to process. To avoid
losing info about other interrupt instances call the parsing function
directly from high IRQ when current work hasn't finished and avoid
accessing SQ_EDC_INFO in that case.

v2:
Simplify high IRQ and BH handlers synchronization using work_pending.
Remove {READ,WRITE}_ONCE notations since smp_{r,w}mb are implicit
compiler barriers.

v3:
Remove exlicit memory barriers as scedule_work has r/w barriers.

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>