apple-gmux: Fix kconfig dependencies

Fix the dependencies of apple-gmux to prevent it from being built-in
when one or more of its dependencies is built as a module. Otherwise it
can fail to build due to missing symbols.

v2: Add dependency on ACPI to fix build failure when ACPI=n

Reported-by: Arun Raghavan <arun.raghavan@collabora.co.uk>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>