setserial: fix build with 2.6.33+ kernel headers on x86

linux/hayesesp.h got removed in 2.6.33, but some archs (like x86) still
define the TIOCGHAYESESP ioctl, breaking the build.

It's very unlikely to be of interest anymore, so just undef it.

Reported-by: Paulius Zaleckas <paulius.zaleckas@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>