Avoid xinput pad jitter resetting axis state

Should take care of #5526.

AFAIK DirectInput preapplies the deadzone so it isn't a problem there.  Not sure if this problem exists for Android controllers/etc.

Example: suppose analog was jittering near 1,0,1 (all below threshold.)  Each jitter would reset axis position to 0, even if you held down an arrow key on the keyboard (or even another button on the controller.)

-[Unknown]