input: ft5x06_ts: correct the status of the pocket mode

Do not need to call function to enter pocket mode if the touch
panel is already in pocket mode as well as no need to call function
to leave pocket mode if it is not in pocket mode.

Change-Id: Ic26376bebeba8e7f0dd37ef3bfbbed36c621604b
Signed-off-by: Mao Li <maol@codeaurora.org>