test/sigfd-deadlock: skip test if poll returns -EOPNOTSUPP
test/sigfd-deadlock: skip test if poll returns -EOPNOTSUPP

Some kernels may disable IORING_OP_POLL support for signalfd and Binder
file descriptors via the Stable commit fc78b2fc21f1
("io_uring: disable polling pollfree files"). Skip the test for this
case.

Signed-off-by: David Disseldorp <589a549dc9f982d9f46aeeb82a09ab6d87ccf1d8@suse.de>

axboe/liburing,axboe/liburing,axboe/liburing