sfc: fix error code in efx_devlink_info_running_versions()

Return -EIO if efx_mcdi_rpc() doesn't return enough space.

Fixes: 14743ddd2495 ("sfc: add devlink info support for ef100")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Edward Cree <ecree.xilinx@gmail.com>
Link: https://patch.msgid.link/afGpsbLRHL4_H0KS@stanley.mountain
Signed-off-by: Paolo Abeni <pabeni@redhat.com>