apparmor: fixup return comments for kernel doc cleanups by Gaosheng Cui

[PATCH -next 05/11] apparmor: Fix kernel-doc warnings in apparmor/label.c
missed updating the Returns comment for the new parameter names

[PATCH -next 05/11] apparmor: Fix kernel-doc warnings in apparmor/label.c
Added the @size parameter comment without mentioning it is a return
value.

Signed-off-by: John Johansen <john.johansen@canonical.com>