net: marvell: prestera: fix compilation with CONFIG_BRIDGE=m

With CONFIG_BRIDGE=m the compilation fails:

    ld: drivers/net/ethernet/marvell/prestera/prestera_switchdev.o: in function `prestera_bridge_port_event':
    prestera_switchdev.c:(.text+0x2ebd): undefined reference to `br_vlan_enabled'

in case the driver is statically enabled.

Fix it by adding 'BRIDGE || BRIDGE=n' dependency.

Fixes: e1189d9a ("net: marvell: prestera: Add Switchdev driver implementation")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Vadym Kochan <vadym.kochan@plvision.eu>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Link: https://lore.kernel.org/r/20201106161128.24069-1-vadym.kochan@plvision.euSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/marvell/prestera/Kconfig

@@ -6,6 +6,7 @@
 config PRESTERA
 	tristate "Marvell Prestera Switch ASICs support"
 	depends on NET_SWITCHDEV && VLAN_8021Q
+	depends on BRIDGE || BRIDGE=n
 	select NET_DEVLINK
 	help
 	  This driver supports Marvell Prestera Switch ASICs family.