powerpc: Use get_signal() signal_setup_done()

powerpc: Use get_signal() signal_setup_done()

commit 129b69df9c9074750245fca8aa92df5cc1a86ef4 upstream.

Use the more generic functions get_signal() signal_setup_done()
for signal delivery.
This inverts also the return codes of setup_*frame() to follow the
kernel convention.

Signed-off-by: Richard Weinberger <richard@nod.at>
[bwh: Backported to 3.16 as dependency of commit 35634ffa1751
 "signal: Always notice exiting tasks"]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>