KEYS: Provide software public key query function [ver #2]

KEYS: Provide software public key query function [ver #2]

Provide a query function for the software public key implementation.  This
permits information about such a key to be obtained using
query_asymmetric_key() or KEYCTL_PKEY_QUERY.

Signed-off-by: David Howells <[email protected]>
Tested-by: Marcel Holtmann <[email protected]>
Reviewed-by: Marcel Holtmann <[email protected]>
Reviewed-by: Denis Kenzior <[email protected]>
Tested-by: Denis Kenzior <[email protected]>
Signed-off-by: James Morris <[email protected]>