KVM: PPC: fix exit accounting for SPRs, tlbwe, tlbsx

The exit type setting for mfspr/mtspr is moved from 44x to toplevel SPR
emulation.  This enables it on e500, and makes sure that all SPRs
are covered.

Exit accounting for tlbwe and tlbsx is added to e500.

Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>