mfd: Check ACPI device companion before checking resources

Current code in mfd-core calls into ACPI to check resources even
on a system that booted with a DT (on kernels with both DT and ACPI
support compiled in). This triggers ACPI exceptions since we may
end up calling the ACPI interpreter when it has not been initialized:

"ACPI Exception: AE_BAD_PARAMETER, Thread 2064154624 could not acquire
Mutex [0x1] (20150410/utmutex-285)"

This patch fixes the issues by adding a check for an ACPI companion
device before carrying out ACPI resources checks to avoid calling
the ACPI interpreter if the fwnode representing the device is an OF one.

Cc: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>