tp: fixed TP velocity target behavior

After fixing the last issue with tpGetRealTargetVelocity and
tpGetMaxTargetVelocity functions, the target velocity was artificially
limited to the cartesian vLimit, even for a rotary move. Now the target
velocity is no longer limited for this case. Furthermore, the
pre-calculated target velocity for spindle-synchronized motion is now
preserved (instead of being overridden by the cartesian limit).
uspace: RT-harden before handling commandline

Otherwise, as observed by dgarr, rtapi_app would crash when the first
hal command was 'loadrt hal_parport cfg="0x378 in"', which executes an
inb() in its setup code.