[IPV6]: Make ip6_route_init to return an error code.

[IPV6]: Make ip6_route_init to return an error code.

The route initialization function does not return any value to notify
if the initialization is successful or not. This patch checks all
calls made for the initilization in order to return a value for the
caller.

Unfortunately, proc_net_fops_create will return a NULL pointer if
CONFIG_PROC_FS is off, so we can not check the return code without an
ifdef CONFIG_PROC_FS block in the ip6_route_init function.

Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Acked-by: Benjamin Thery <benjamin.thery@bull.net>
Signed-off-by: David S. Miller <davem@davemloft.net>