docs: Document the real behaviour of suspend-to-{mem,disk}
docs: Document the real behaviour of suspend-to-{mem,disk}

We get a question every now and then about why hibernation works when
suspend-to-disk is disabled and similar.  Let's hope that, by documenting the
obvious more blatantly, people will get more informed.

Signed-off-by: Martin Kletzander <e82f23e74d43760279ebcc505dac4ae70d5627d0@redhat.com>
Reviewed-by: Erik Skultety <2c14d38fa47c8799f1b9c16280abe27f8edfec6e@redhat.com>

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