input: touchscreen: bu21150: ensure proper mode transition

This change ensures that the touch AFE (Analog Front End) transitions
to the right mode and touch/display functionality isn't interrupted
in a special use case.

When touch-to-wake is enabled and AFE is in gesture self capacitance
mode, if the user makes an invalid gesture, the AFE will transition
to gesture mutual capacitance mode. Since the gesture is invalid, it
will not end up waking up the device. After the specified timeout,
touch SW will instruct the AFE to go back to gesture self capacitance
mode. At the same time, if the user presses the power key to resume,
both AFE driver's resume function and touch SW in user space are
trying to update the same AFE register with different values. We need
to make sure that the update by the resume function prevails. This
directly impacts whether display and touch will work properly upon
resume.

Change-Id: Ia3a857efe4d6ea82442dc4fe2a73f6e6ea97d84d
Signed-off-by: Jing Lin <jinglin@codeaurora.org>
Signed-off-by: Chun Zhang <chunz@codeaurora.org>