There is no need to keep around a pointer to a dentry when all it is
used for is to remove the debugfs file when tearing things down.  As the
name is simple, have debugfs look up the dentry when removing things,
keeping the logic much simpler.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20210216142400.3759099-1-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>