ANDROID: add vendor fields to swap_slots_cache to support multiple swap devices

struct swap_slots_cache  :: ANDROID_VENDOR_DATA(1)
1) Multiple swap devices can be supported;
2) There are different kinds of data;
3) During data reclamation, different types of data are exchanged
   to different swap devices;
4) Each swap device has corresponding arrays of slots and slots_ret;
5) Each swap device has corresponding indexes of nr, cur and n_ret;
6) This field is a pointer, it points to a struct which contains
   all the other arrays and indexes;

Bug: 225795494
Change-Id: Icf116135926be98449a2d96fc458e58e5ad3b7e9
Signed-off-by: Bing Han <bing.han@transsion.com>