[ARM] pxa/hx4700: fix hx4700 touchscreen pressure values

hx4700 touchscreen events were being dropped in ads7846_rx() because their
pressure values consistently exceeded the platform maximum of 512; a sample
of 256 pressure values were in the range 531 to 815.  Doubling the platform
maximum to 1024 allows hx4700 touchscreen events to pass the test.
Signed-off-by: Paul Parsons <lost.distance@yahoo.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>

arch/arm/mach-pxa/hx4700.c

@@ -604,7 +604,7 @@ static struct platform_device gpio_vbus = {
 static const struct ads7846_platform_data tsc2046_info = {
 	.model            = 7846,
 	.vref_delay_usecs = 100,
-	.pressure_max     = 512,
+	.pressure_max     = 1024,
 	.debounce_max     = 10,
 	.debounce_tol     = 3,
 	.debounce_rep     = 1,