netdevsim: fib: Add dummy implementation for FIB offload

Implement dummy IPv4 and IPv6 FIB "offload" in the driver by storing
currently "programmed" routes in a hash table. Each route in the hash
table is marked with "trap" indication. The indication is cleared when
the route is replaced or when the netdevsim instance is deleted.

This will later allow us to test the route offload API on top of
netdevsim.

v2:
* Convert to new fib_alias_hw_flags_set() interface
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/Kconfig

@@ -549,6 +549,7 @@ source "drivers/net/hyperv/Kconfig"
 config NETDEVSIM
 	tristate "Simulated networking device"
 	depends on DEBUG_FS
+	depends on IPV6 || IPV6=n
 	select NET_DEVLINK
 	help
 	  This driver is a developer testing tool and software model that can