tests: kernel: poll: Disable on qemu_arc_hs6x

This commit disables the `kernel.poll` test on `qemu_arc_hs6x` because
it fails at run-time when compiled with GCC 12.

Revert this commit when the GitHub issue #49492, which tracks this bug,
is fixed.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>