HISI LPC: Add Kconfig MFD_CORE dependency

For ACPI support of the HiSilicon LPC driver we depend
on MFD_CORE config.

Currently the HiSi LPC Kconfig entry does not define this
dependency, so add it.

The reason for depending on MFD_CORE in the driver is
that we model the LPC host as an MFD, in that a platform
device will be created for each device on the bus.

We do this as we need to modify the resources of these
derived platform devices, something which we should not
do to the original devices created in the ACPI scan.
Details in e0aa1563 ("HISI LPC: Add ACPI support").

Fixes: e0aa1563

 ("HISI LPC: Add ACPI support")
Reported-and-tested-by: Tan Xiaojun <tanxiaojun@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>