HACK: don't even check for termiox

termiox was removed from linux in e0efb3168d34
Some more information available in https://www.spinics.net/lists/linux-serial/msg41926.html

Attempting to use the termiox ioctls on more modern kernels results in
"Inappropriate IOCTL" errors.

While the "right" solution might be to remove the termiox code from the
linux path, simply not checking for termiox builds a libserialport that
functions on modern linux kernels.

Signed-off-by: Karl Palsson <redacted>