HV: hv_balloon: fix memory leak with using debugfs_lookup()
In the Linux kernel, the following vulnerability has been resolved:

HV: hv_balloon: fix memory leak with using debugfs_lookup()

When calling debugfs_lookup() the result must have dput() called on it,
otherwise the memory will leak over time.  To make things simpler, just
call debugfs_lookup_and_remove() instead which handles all of the logic
at once.