staging: greybus: loopback_test: fix poll-mask build breakage

staging: greybus: loopback_test: fix poll-mask build breakage

A scripted conversion from userland POLL* to kernel EPOLL* constants
mistakingly replaced the poll flags in the loopback_test tool, which
therefore no longer builds.

Fixes: a9a08845e9ac ("vfs: do bulk POLL* -> EPOLL* replacement")
Cc: stable <stable@vger.kernel.org>     # 4.16
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20200312110151.22028-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>