Trying to use lindebugfs for debugging wirless drivers two issues
became apparent:
(a) a pnic in lindebugfs calling a hard coded release function if the
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.
(b) In LinuxKPI simple_read_from_buffer() would call copy_to_user() but
buffers weren't setup for this (lindebugfs has 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].
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks