KVM: PPC: Book3S PR: Refactor program interrupt related code into separate function

The function kvmppc_handle_exit_pr() is quite huge and thus hard to read,
and even contains a "spaghetti-code"-like goto between the different case
labels of the big switch statement. This can be made much more readable
by moving the code related to injecting program interrupts / instruction
emulation into a separate function instead.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>