kernel: Add get_available mdev callback (fix leaked available_instances)

The mdev core's shared parent->available_instances counter leaks whenever
an mdev remove path fails to complete (as happened during the now-fixed
remove crash): creates then fail with -EUSERS while sysfs reports 0
available instances with zero mdevs present.

Implement mdev_driver.get_available to compute availability from the
driver's own authoritative device list instead of the core counter.
Handles the 'nvidia-' prefixed sysfs type names when looking up per-type
max_instances (falls back to 1).

0 files changed, 0 insertions, 0 deletions