KEYS: Document asymmetric key type
David Howells authored

In-source documentation for the asymmetric key type.  This will be located in:

	Documentation/crypto/asymmetric-keys.txt
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
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