GCC generates type limit warnings when comparison is always true or
always false due to the limited range of the data type, This was in a
termios structure. For most of the cases in RTEMS, this was when
a variable of an unsigned type was compared to be < or <= 0.
GCC currently has issues with false positive warnings about array bounds
violations when the value used as the index is a pointer. This slightly
reworks the code to make it cleaner and to avoid this warning.
