target-alpha: fix termbits and target IOC macros

This patch fixes the two following problems for Alpha linux-user:
   - termbits.h is incorrectly using host IOC macros and structures
   - IOC bitfields sizes are incorrectly set

This patch corrects the ioctl TCGETS done by isatty function call
on Alpha (when running SPEC crafty for instance).

Signed-off-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5704 c046a42c-6fe2-441c-8c8c-71466251a162
