drivercore: Output common devicetree information in uevent

When userspace needs to find a specific device, it currently isn't easy to
resolve a /sys/devices/ path from a specific device tree node.  Nor is it
easy to obtain the compatible list for devices.

This patch generalizes the code that inserts OF_* values into the uevent
device attribute so that any device that is attached to an OF node will
have that information exported to userspace.  Without this patch only
platform devices and some powerpc-specific busses have access to this
data.

The original function also creates a MODALIAS property for the compatible
list, but that code has not been generalized into the common case because
it has the potential to break module loading on a lot of bus types.  Bus
types are still responsible for their own MODALIAS properties.

Boot tested on ARM and compile tested on PowerPC and SPARC.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tobias ...