net: b53: enable BPDU reception for management port

For STP to work, receiving BPDUs is essential, but the appropriate bit
was never set. Without GC_RX_BPDU_EN, the switch chip will filter all
BPDUs, even if an appropriate PVID VLAN was setup.

Fixes: ff39c2d6 ("net: dsa: b53: Add bridge support")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Link: https://patch.msgid.link/20250414200434.194422-1-jonas.gorski@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>