modules: lvgl: Fix coordinate handling for invert-{x,y} and swap-xy

This patch fixes two issues in the coordinate handling of the
`zephyr,lvgl-pointer-input` compatible:
- If the swap-xy flag is set the coordinates need to be swapped even
  before the sync event is received.
- The coordinates are stored into an additional variable instead of the
  pending_event. This is done to prevent the double inversion for touch
  release events.

Resolves issue #70539.

Signed-off-by: Fabian Blatz <fabianblatz@gmail.com>