iio: proximity: sx9500: Fix proximity value

Because of the ABI confusion proximity value exposed by SX9500
was inverted.

Signed-off-by: Daniel Baluta <[e-mail]>
Reviewed-by: Vlad Dogaru <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/proximity/sx9500.c

···
 	if (ret < 0)
 		return ret;
 
-	*val = 32767 - (s16)be16_to_cpu(regval);
+	*val = be16_to_cpu(regval);
 
 	return IIO_VAL_INT;
 }