staging: fieldbus: Fix build error without CONFIG_REGMAP_MMIO

staging: fieldbus: Fix build error without CONFIG_REGMAP_MMIO

Fix gcc build error while CONFIG_REGMAP_MMIO is not set

drivers/staging/fieldbus/anybuss/arcx-anybus.o: In function `controller_probe':
arcx-anybus.c: undefined reference to `__devm_regmap_init_mmio_clk'

Select REGMAP_MMIO to fix it.

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 2411a336c8ce ("staging: fieldbus: arcx-anybus: change custom -> mmio regmap")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Sven Van Asbroeck <TheSven73@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>