net: sparx5: uses, depends on BRIDGE or !BRIDGE

Fix build errors when BRIDGE=m and SPARX5_SWITCH=y:

riscv64-linux-ld: drivers/net/ethernet/microchip/sparx5/sparx5_switchdev.o: in function `.L305':
sparx5_switchdev.c:(.text+0xdb0): undefined reference to `br_vlan_enabled'
riscv64-linux-ld: drivers/net/ethernet/microchip/sparx5/sparx5_switchdev.o: in function `.L283':
sparx5_switchdev.c:(.text+0xee0): undefined reference to `br_vlan_enabled'

Fixes: 3cfa11ba ("net: sparx5: add the basic sparx5 driver")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Cc: Horatiu Vultur <horatiu.vultur@microchip.com>
Cc: Lars Povlsen <lars.povlsen@microchip.com>
Cc: Steen Hegelund <Steen.Hegelund@microchip.com>
Cc: UNGLinuxDriver@microchip.com
Cc: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/20220330012025.29560-1-rdunlap@infradead.org


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