This fixes:
ERROR: "switch_generic_set_link" [drivers/net/phy/b53/b53_common.ko] undefined!
At some point all packages for swconfig drivers were dropped and targets
were meant to have them built into kernels. It seems b53 (re-)gained its
kmod-switch-bcm53xx however and b53 needs to be built as module.
Fixes: b2cfed48f626 ("Revert "swconfig: fix Broadcom b53 support"")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>