input: touchscreen: bu21150: set AFE to standby mode before resume

When device wakes up from suspend, register write for AFE enablement
will cause signal change on AFE. In this case, HAL library thinks
there are touch events on the screen and reports ghost touch. Setting
AFE to standby mode during resume process lets AFE ignore signal
changes during resume sequence.

Change-Id: Idebeb4c2c2119104ea64ccbefe79b1d3c98052e3
Signed-off-by: Chun Zhang <chunz@codeaurora.org>