ARM: OMAP: fix the ads7846 init code

In case a board provides the gpio_pendown and not board_pdata,
the GPIO debounce is not taken care of.
Fix this by taking care of GPIO debounce in any case.

Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: Tony Lindgren <tony@atomide.com>