simplify and improve BOARD_USE_LEGACY_TOUCHSCREEN

in addition to converting ABS_MT_TOUCH_MAJOR to ABS_MT_PRESSURE, it also converts ABS_MT_WIDTH_MAJOR to ABS_MT_TOUCH_MAJOR.

also add 2 workarounds for some touchscreen driver which
 1. has BTN_TOUCH feature but it doesn't send BTN_TOUCH event
 2. sends multi-touch event for not-in-use pointer

reference: http://source.android.com/tech/input/touch-devices.html

Change-Id: I7b7f8802e45bf9d9f8de00373559a30ea839a178