kunit: Add APIs for managing devices

Tests for drivers often require a struct device to pass to other
functions. While it's possible to create these with
root_device_register(), or to use something

kunit: Add APIs for managing devices

Tests for drivers often require a struct device to pass to other
functions. While it's possible to create these with
root_device_register(), or to use something like a platform device, this
is both a misuse of those APIs, and can be difficult to clean up after,
for example, a failed assertion.

Add some KUnit-specific functions for registering and unregistering a
struct device:
- kunit_device_register()
- kunit_device_register_with_driver()
- kunit_device_unregister()

These helpers allocate a on a 'kunit' bus which will either probe the
driver passed in (kunit_device_register_with_driver), or will create a
stub driver (kunit_device_register) which is cleaned up on test shutdown.

Devices are automatically unregistered on test shutdown, but can be
manually unregistered earlier with kunit_device_unregister() in order
to, for example, test device release code.

Reviewed-by: Matti Vaittinen <[email protected]>
Reviewed-by: Maxime Ripard <[email protected]>
Signed-off-by: David Gow <[email protected]>
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Shuah Khan <[email protected]>

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