Build error when crypto and swcrypto are omitted from kernel

[Paul Goyette <paul%whooppee.com@localhost>]

With the recent introduction of swap encryption, it is now mandatory
to include "pseudo-device crypto" and/or "pseudo-device swcrypto" in
the kernel.  Without this, the kernel fails to link, with undefined
references to several symbols:
	rijndael_cipherInit
	rijndael_blockEncrypt
	rijndael_blockDecrypt
	rijndael_makeKey

Since the two crypto devices are optional (and run-time loadable)
components of the kernel, it seems to me that encrypted-swap should
also be optional.


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