devlink: fix the name of eswitch commands

The eswitch_[gs]et command is supposed to be similar to port_[gs]et
command - for multiple eswitch attributes. However, when it was introduced
by 08f4b591

 ("net/devlink: Add E-Switch mode control") it was wrongly
named with the word "mode" in it. So fix this now, make the oririnal
enum value existing but obsolete.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>