ANDROID: mm: use raw seqcount variants in vm_write_*

write_seqcount_begin expects to be called from a non-preemptible
context to avoid preemption by a read section that can spin due
to an odd value. But the readers of vm_sequence never retries and
thus writers need not disable preemption. Use the non-lockdep
variant as lockdep checks are now in-built to write_seqcount_begin.

Bug: 161210518
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Change-Id: If4f0cddd7f0a79136495060d4acc1702abb46817