sysfs:Addresses documentation in sysfs_merge_group and sysfs_unmerge_group.

These functions take a struct attribute_group as an input which has an
optional .name field. These functions rely on the .name field being
populated and do not check if its null. They pass this name into other
functions, eventually leading to a null pointer dereference.

This change simply updates the documentation of the function to make
this requirement clear.

Signed-off-by: Rohan Kollambalath <rkollamb@digi.com>
Link: https://lore.kernel.org/r/20240211223634.2103665-1-rohankollambalath@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>