net: bridge: fix br_vlan_get_{pvid,info} return values

These two functions return the regular -EINVAL failure in the normal
code path, but return a nonstandard '-1' error otherwise, which gets
interpreted as -EPERM.

Let's change it to -EINVAL for the dummy functions as well.

Fixes: 4d4fd361

 ("net: bridge: Publish bridge accessor functions")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>