ANDROID: mm: madvise: Avoid counting swap entry references for migration entries

Race between the madvise(PAGEOUT) and migration caused by page offline
can make the swp_swapcount()->_swap_info_get emitting the "Bad swap file
entry " message because it is trying to get the info on the migration
entry. Add check if it is a migration entry.

Bug: 356032508
Bug: 357771059
Fixes: aee36dd5 ("ANDROID: mm: add vendor hooks in madvise for swap entry")
Change-Id: Ia209d2a0103ac506ceae8fd71f733c1dc85443a6
Signed-off-by: Charan Teja Kalla <quic_charante@quicinc.com>
Signed-off-by: Nikhil V <quic_nprakash@quicinc.com>
(cherry picked from commit 7d0a1d6b)