Input: of_touchscreen - add support for inverted / swapped axes

Extend touchscreen_parse_properties() with support for the
touchscreen-inverted-x/y and touchscreen-swapped-x-y properties and
add touchscreen_set_mt_pos() and touchscreen_report_pos() helper
functions for storing coordinates into a input_mt_pos struct, or
directly reporting them, taking these properties into account.

This commit also modifies the existing callers of
touchscreen_parse_properties() to pass in NULL for the new third
argument, keeping the existing behavior.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>