arm: bcmbca: replace ARCH_BCM6753 symbols in Kconfig with BCM6855

As CONFIG_ARCH_BCM6753 is replaced with CONFIG_BCM6855, update the
driver Kconfig to use the new config symbol.

Signed-off-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: Philippe Reynes <philippe.reynes@softathome.com>