CHROMIUM: input: cyapa - fix power mode switch problems

CHROMIUM: input: cyapa - fix power mode switch problems

We have found that some commands may fail if the touchpad is
not running at the full mode. Moreover, setting new power modes
would take the amount of time roughly equal to the old scanrate
to complete. The patch fixes several places where the unsafe
commands might be run before completely returning to the full
mode. Meanwhile, the cyapa_set_power_mode function now returns
early if the mode to set is the same as the current one.

Signed-off-by: Tai-Hsu Lin <sheckylin@chromium.org>
BUG=chromium:196520
TEST=Repeatedly suspend/resume the device with Cypress touchpad for
a few hundred times. One should see errors about reading query data
in the /var/log/messages.

With the fix, one shouldn't see the error.

Change-Id: I95a843a077d5840c57cc24daf85b6549550fa73d
Reviewed-on: https://gerrit.chromium.org/gerrit/46115
Reviewed-by: Benson Leung <bleung@chromium.org>
Commit-Queue: Tai-Hsu Lin <sheckylin@chromium.org>
Tested-by: Tai-Hsu Lin <sheckylin@chromium.org>