drm/amdgpu: check context id for context switching (v2)

check the filp is not robust, and sometimes different contexts may
have same filp value.

v2: check both filp and ctx_id

Signed-off-by: Jammy Zhou <Jammy.Zhou@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

@@ -945,6 +945,7 @@ struct amdgpu_ring {
 	unsigned		next_rptr_offs;
 	unsigned		fence_offs;
 	struct drm_file		*current_filp;
+	unsigned		current_ctx;
 	bool			need_ctx_switch;
 	enum amdgpu_ring_type	type;
 	char			name[16];