ANDROID: PM / Domains: add vendor_hook to disallow domain idle state

In order to debug critical domain and device power issues, it may be
necessary to disallow certain idle states at runtime. Enable a vendor
hook to check if a domain idle state is allowed for powering down the
domain.

Bug: 175718935
Bug: 195914333
Change-Id: I403c0c7d272439fb338bbf54a346861559385047
Signed-off-by: Lina Iyer <ilina@codeaurora.org>
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>