Input: wm97xx - drop out of range inputs

With fast movements, there occured some out of screen jumps with my
touchscreen. The abs_x and abs_y module parameters should fix this by
default, but the driver doesn't actively checks the x/y coordinates.

Instead it seems that the input layer was supposed to drop out of range
inputs, as described in the comments:
"These parameters are used to help the input layer discard out of
range readings and reduce jitter etc"

The input layer documentation describes that values that are not in the
absolute range are also accepted.

So this patch adds a check within the driver.

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>