gpio: omap: remove dataout variation in context handling

When a GPIO block has the set/clear dataout registers implemented, it
also has the normal dataout register implemented. Reading this register
reads the current GPIO output state, and writing it sets the GPIOs to
the explicit state. This is the behaviour that we want when saving and
restoring the context, so use the dataout register exclusively.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>