powerpc/83xx: enable EPOLL syscall in defconfig

83xx users looking to run apache will experience this error:

/var/log/apache2/error.log:
[emerg] (38)Function not implemented: Couldn't create pollset in child; check system or user limits

enabling CONFIG_EPOLL in kernel config fixes this so apache can run.

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>