hcrypto: don't redefine key_type

hcrypto: don't redefine key_type

Linux's keyring code uses "struct key_type", which is also used
internally by the hcrypto code. As, on some Linux variants,
afs/sysincludes.h ends up including the keyring definitions, we
need to rename our internal key_type definition to something
that doesn't clash.

Change-Id: Ibfb968db0db3e80d877881fc6da4b34428ee382f
Reviewed-on: http://gerrit.openafs.org/4192
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Tested-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Reviewed-by: Derrick Brashear <shadow@dementia.org>