ANDROID: GKI: Swap Allocator ABI Fixup

Restore the include/linux/swap.h to it's state before FROMLIST
allocator patches (aosp/3164822, aosp/3164823) -- Revert to using
bit fields instead of u[8|16] and restore the CLUSTER_STATE_*
defines in swap.h; in order to maintain ABI compatibility.

Change-Id: I7cec72d12ca1ac07c012d9cdfcdac4667ef4d132
Signed-off-by: Chris Li <chrisl@kernel.org>
Bug: 313807618
Bug: 351082780
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>