net: hsr: Use full string description when opening HSR network device

Up till now only single character ('A' or 'B') was used to provide
information of HSR slave network device status.

As it is also possible and valid, that Interlink network device may
be supported as well, the description must be more verbose. As a result
the full string description is now used.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>