target/ppc: add SMT support to msgsnd broadcast

msgsnd has a broadcast mode that sends hypervisor doorbells to all
threads belonging to the same core as the target. A "subcore" mode
sends to all or one thread depending on 1LPAR mode.

Reviewed-by: Glenn Miles <milesg@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
4 files changed