gpio/omap: ensure gpio context is initialised

Commit a2797bea (gpio/omap: force restore if context loss is not
detectable) broke gpio support for OMAP when booting with device-tree
because a restore of the gpio context being performed without ever
initialising the gpio context. In other words, the context restored was
bad.

This problem could also occur in the non device-tree case, however, it
is much less likely because when booting without device-tree we can
detect context loss via a platform specific API and so context restore
is performed less often.

Nevertheless we should ensure that the gpio context is initialised
on the first pm-runtime resume for gpio banks that could lose their
state regardless of whether we are booting with device-tree or not.

The context loss count was being initialised on the first pm-runtime
suspend following a resume, by populating the get_count_loss_count()
function pointer after the first pm-runtime resume. To make the code
more readable and logical, initialise the context loss count on the
first pm-runtime resume if the context is not yet valid.

Reported-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh <Shilimkar&lt;santosh.shilimkar@ti.com>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>