Input: ti_am335x_tsc - ack pending IRQs at probe and before suspend

It is seen that just enabling the TSC module triggers a HW_PEN IRQ
without any interaction with touchscreen by user. This results in first
suspend/resume sequence to fail as system immediately wakes up from
suspend as soon as HW_PEN IRQ is enabled in suspend handler due to the
pending IRQ. Therefore clear all IRQs at probe and also in suspend
callback for sanity.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Vignesh R <vigneshr@ti.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>