reset: Add of_reset_control_get

In some cases, you might need to deassert from reset an hardware block that
doesn't associated to a struct device (CPUs, timers, etc.).

Add a small helper to retrieve the reset controller from the device tree
without the need to pass a struct device.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
(cherry picked from commit fc0a5921561c71be2c334a335c1680f7930434d7)

Signed-off-by: Chang Rebecca Swee Fun <rebecca.swee.fun.chang@intel.com>
reset: Add optional resets and stubs

This patch adds device_reset_optional and (devm_)reset_control_get_optional
variants that drivers can use to indicate they can function without control
over the reset line. For those functions, stubs are added so the drivers can
be compiled with CONFIG_RESET_CONTROLLER disabled.
Also, device_reset is annotated with __must_check. Drivers ignoring the return
value should use device_reset_optional instead.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
(cherry picked from commit b424080a9e086e683ad5fdc624a7cf3c024e0c0f)

Signed-off-by: Chang Rebecca Swee Fun <rebecca.swee.fun.chang@intel.com>
reset: Add of_reset_control_get to reset.h

of_reset_control_get is not declared static in drivers/reset/core.c, which
is correct as we want to use it elsewhere too. But it does not have a
protype declared anywhere under include/linux. Add a prototype / stub for it
to linux/reset.h to fix this.

Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
(cherry picked from commit e3ec0a8c6eea4f22d5468f01c065caca4dd1ecca)

Signed-off-by: Chang Rebecca Swee Fun <rebecca.swee.fun.chang@intel.com>
Staging: remove lttng from staging driver

Fix build error for LTSI v3.14 kernel source tree.

Signed-off-by: Chang Rebecca Swee Fun <rebecca.swee.fun.chang@intel.com>