net: dsa: loop: Add module soft dependency

There is a soft dependency against dsa_loop_bdinfo.ko which sets up the
MDIO device registration, since there are no symbols referenced by
dsa_loop.ko, there is no automatic loading of dsa_loop_bdinfo.ko which
is needed.

Fixes: 98cd1552ea ("net: dsa: Mock-up driver")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/dsa_loop.c

@@ -360,6 +360,7 @@ static void __exit dsa_loop_exit(void)
 }
 module_exit(dsa_loop_exit);
 
+MODULE_SOFTDEP("pre: dsa_loop_bdinfo");
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Florian Fainelli");
 MODULE_DESCRIPTION("DSA loopback driver");