ethdev: rename a flow shared action error code

ethdev: rename a flow shared action error code

In the experimental function rte_flow_shared_action_destroy()
introduced in DPDK 20.11, the errno ETOOMANYREFS was used.
This errno is not always available on Windows,
so it is preferred using EBUSY instead.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Reviewed-by: Tal Shnaiderman <talshn@nvidia.com>
Tested-by: Tal Shnaiderman <talshn@nvidia.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>