Staging: mrst_touchscreen - more fixes

Changes:

 - switch to use threaded IRQ
 - more __devinit/__devexit annotations
 - rely on input core to remove jitter from events
 - global pointer removed
 - NEC/MAXIM/Freescale handling factored out

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>