ACPI: SoC: APD: Check return value of acpi_dev_get_property()

`fch_misc_setup()` uses `acpi_dev_get_property()` to read the value of
"is-rv" passed in by BIOS in ACPI tables. However, not all BIOSes
might pass in this property and hence it is important to first check
the return value of `acpi_dev_get_property()` before referencing the
object filled by it.

Signed-off-by: Furquan Shaikh <furquan@google.com>
[ rjw: Subject edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>