platform/x86: apple-gmux: Make PCI dependency explicit

After commit 5d32a665 (PCI/ACPI: Allow ACPI to be built without
CONFIG_PCI set) dependencies on CONFIG_PCI that previously were
satisfied implicitly through dependencies on CONFIG_ACPI have to be
specified directly.

This driver depends on the PCI infrastructure but the dependency has
not been called out explicitly yet.

Fixes: 5d32a665 ("PCI/ACPI: Allow ACPI to be built without CONFIG_PCI set")
Signed-off-by: Sinan Kaya <okaya@kernel.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>