caller had not provided one.  This seems to be based on assumptions
that no longer hold up.  Remove the hard coded release function to
prevent panics.

buffers weren't setup for this (lindebugfs copies data from its
own buffer) and then pseudofs will do another copyout to the user
on this;  remove the copy_to_user() and simply copy the data over
to the provided buffer; this works for as long as the only consumers
remain debugfs callers (which currently seems to be the case).
[the only out-of-tree consumers I am aware off are two drm-kmod
drivers/gpu/drm/amd/pm/* debugfs functions I cannot test].