KVM: PPC: Book3S PR: Fix failure status setting in treclaim. emulation

The treclaim. emulation needs to record failure status in the TEXASR
register if the transaction had not previously failed.  However, the
current code first does kvmppc_save_tm_pr() (which does a treclaim.
itself) and then checks the failure summary bit in TEXASR after that.
Since treclaim. itself causes transaction failure, the FS bit is
always set, so we were never updating TEXASR with the failure cause
supplied by the guest as the RA parameter to the treclaim. instruction.
This caused the tm-unavailable test in tools/testing/selftests/powerpc/tm
to fail.

To fix this, we need to read TEXASR before calling kvmppc_save_tm_pr(),
and base the final value of TEXASR on that value.

Fixes: 03c81682

 ("KVM: PPC: Book3S PR: Add emulation for treclaim.")
Reviewed-by: Simon Guo <wei.guo.simon@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>