SEC h/w versions 2.1 and above support sha224 via explicit instruction.

Performing sha224 ahashes on earlier versions is still possible because
they support sha256 (sha224 is sha256 with different initial constants
and a different truncation length).  We do this by overriding hardware
context self-initialization, and perform it manually in s/w instead.

Thanks to Lee for his fixes for correct execution on actual sec2.0 h/w.
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off by: Lee Nipper <lee.nipper@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>