KVM: PPC: Book3S HV: Pull out TM state save/restore into separate procedures

commit f024ee09 upstream.

This moves the transactional memory state save and restore sequences
out of the guest entry/exit paths into separate procedures.  This is
so that these sequences can be used in going into and out of nap
in a subsequent patch.

The only code changes here are (a) saving and restore LR on the
stack, since these new procedures get called with a bl instruction,
(b) explicitly saving r1 into the PACA instead of assuming that
HSTATE_HOST_R1(r13) is already set, and (c) removing an unnecessary
and redundant setting of MSR[TM] that should have been removed by
commit 9d4d0bdd9e0a ("KVM: PPC: Book3S HV: Add transactional memory
support", 2013-09-24) but wasn't.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
[bwh: Backported to 3.16: include dots in subroutine names]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>