kernel/kmod.c: document call_usermodehelper_fns() a bit
kernel/kmod.c: document call_usermodehelper_fns() a bit

This function's interface is, uh, subtle.  Attempt to apologise for it.

Cc: WANG Cong <0f114804888b88d50037b04b42e57b858d851b87@gmail.com>
Cc: Cyrill Gorcunov <7a1ea01eee6961eb1e372e3508c2670446d086f4@openvz.org>
Cc: Kees Cook <50cb10d2be062154b17ab4d66a4eab34f1cf1c84@chromium.org>
Cc: Serge Hallyn <3df611b026e4639bee8aef7a4beb2e39fcebb313@canonical.com>
Cc: "Eric W. Biederman" <8a741aa8cbd77ebc4a56ddb528ce9fd15d42f034@xmission.com>
Cc: Alan Cox <91e38e63b890fbb214c8914809fde03c73e7f24d@lxorguk.ukuu.org.uk>
Cc: Oleg Nesterov <20b70f0af00562e63758b9ee42012ecc96c58590@redhat.com>
Cc: Rusty Russell <df9728c9e5104131c08c7adb03af425394842596@rustcorp.com.au>
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas