gpio/omap: ensure gpio context is initialised

Commit a2797be (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>
Tested-by: Tony Lindgren <tony@atomide.com>
ARM: OMAP2+: only search for GPMC DT child nodes on probe

The GPMC DT probe function use for_each_node_by_name() to search
child device nodes of the GPMC controller. But this function does
not use the GPMC device node as the root of the search and instead
search across the complete Device Tree.

This means that any device node on the DT that is using any of the
GPMC child nodes names searched for will be returned even if they
are not connected to the GPMC, making the gpmc_probe_xxx_child()
function to fail.

Fix this by using the GPMC device node as the search root so the
search will be restricted to its children.

Reported-by: Lars Poeschel <poeschel@lemonage.de>
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
ARM: OMAP2+: only WARN if a GPMC child probe function fail

If any of the GPMC child nodes fails, this shouldn't make the
whole gpmc_probe_dt() function to fail. It is better to just
WARN and allow other devices probe function to succeed.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>