drm/amdgpu: remove excl as shared workarounds

This was added because of the now dropped shared on excl dependency.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20211123142111.3885-15-christian.koenig@amd.com