KVM: PPC: Pass enum to kvmppc_get_last_inst

The kvmppc_get_last_inst function recently received a facelift that allowed
us to pass an enum of the type of instruction we want to read into it rather
than an unreadable boolean.

Unfortunately, not all callers ended up passing the enum. This wasn't really
an issue as "true" and "false" happen to match the two enum values we have,
but it's still hard to read.

Update all callers of kvmppc_get_last_inst() to follow the new calling
convention.

Signed-off-by: Alexander Graf <agraf@suse.de>