drm/amdgpu: Skip coredump during resets for debug

Skip scheduling coredump when gpu reset is intentionally triggered
through debugfs.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Asad Kamal <asad.kamal@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>