input: touchscreen: y771: require low latency

Currently, CPU can enter deep sleep while waiting for data on the i2c
bug. That means an i2c read of 8 bytes can take as long as 10 ms, which
would overrun the desired interrupt handling time.
Use pm qos to require low latency and prevent CPU from entering deep
sleep while handling touch interrupts.

Bug: 110939384
Test: look at the i2c read traces:
1) ./external/chromium-trace/systrace.py --atrace-categories=view,wm,am,app,gfx,i2c,sched,irq,video,power,input,workq,freq
2) perform a fling
3) review the i2c read duration on the touchscreen bus

Change-Id: Icf8ab09324003a85af70517769ced3bae52f705c
Signed-Off-By: Siarhei Vishniakou <svv@google.com>