We have support for the epoll_pwait syscall, but it wasn't enabled for
ARM guests because we hadn't defined the syscall number; correct this
deficiency.
Reported-by: Dave Flogeras <dflogeras2@gmail.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>