When adding platform and AMBA devices, set the device node's device
member to point to it.

This speeds lookups considerably and is safe because we only create one
of these devices for any given device node.

Signed-off-by: Tomeu Vizoso <redacted>
---

Changes in v5:
- Set the pointer to struct device also for AMBA devices
- Unset the pointer to struct device when the platform device is about
  to be unregistered
- Increase the reference count of the device before returning from
  of_find_device_by_node()

 drivers/of/platform.c | 19 ++++++++++---------
 include/linux/of.h    |  1 +
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index 1001efaedcb8..408d89f1d124 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c

@@ -32,11 +32,6 @@ const struct of_device_id of_default_bus_match_table[] = {
        {} /* Empty terminated list */
 };

-static int of_dev_node_match(struct device *dev, void *data)
-{
-       return dev->of_node == data;
-}
-
 /**
  * of_find_device_by_node - Find the platform_device associated with a node
  * @np: Pointer to device tree node

@@ -45,10 +40,10 @@ static int of_dev_node_match(struct device *dev, void *data)
  */
 struct platform_device *of_find_device_by_node(struct device_node *np)
 {
-       struct device *dev;
-
-       dev = bus_find_device(&platform_bus_type, NULL, np, of_dev_node_match);
-       return dev ? to_platform_device(dev) : NULL;
+       if (np->device && np->device->bus == &platform_bus_type &&
+           get_device(np->device))