TouchInputMapper: don't check touchpad touches by screen bounds

Uncaptured touchpads (with DeviceMode::POINTER) still on the old stack
(i.e. the Sony DualShock 4 touchpad) were having touches ignored if they
started at coordinates that would be outside of the bounds of the
touchscreen. Since touchpads use relative motions and don't directly
relate raw touch locations to screen locations, this was incorrect, and
caused touches to be ignored with certain screen/touchpad dimension and
orientation combinations.

Bug: 280396539
Test: connect Sony DualShock 4 by USB, rotate screen to portrait, check
      touches starting in all areas of the pad are turned into pointer
      movements
Test: atest inputflinger_tests
Change-Id: I9a92ba79246ee8fc25418c2e248ae2c3839a0d58