net: dsa: select NET_SWITCHDEV

The support for DSA Ethernet switch chips depends on TCP/IP networking,
thus explicit that HAVE_NET_DSA depends on INET.

DSA uses SWITCHDEV, thus select it instead of depending on it.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>