Grey out scrolling speed slider bar

When ever the mouse scrolling acceleration settings is toggled to
set "enabled", the mouse scrolling speed slider bar should be
greyed out.

Bug: 383555305
Bug: 384795606
Test: Local DUT with aconfig flags enabled, verified settings appears
      and is togglable. Verified toggle affects scrolling acceleration.
Flag: com.android.hardware.input.mouse_scrolling_acceleration
Change-Id: Ib96a4437864a0395c8c185bbd8cfb13f3979c84f