crypto: sun4i-ss - fix large block size support

The run-time self-tests fail quite early, as soon as the input block
size is larger than 64 bytes:

  alg: hash: Test 4 failed for sha1-sun4i-ss
  00000000: b9 c9 1e 52 c0 26 d8 39 81 ff f2 3c 99 b1 27 b2
  00000010: 30 d6 c9 85

One thing to notice is the value of the last word, which is the one
expected (it can sometime be the last two words). The datasheet isn't
very clear about when the digest is ready to retrieve and is seems the
bit SS_DATA_END is cleared when the digest was computed *but* that
doesn't mean the digest is ready to retrieve in the registers.

A ndelay(1) is added before reading the computed digest to ensure it is
available in the SS_MD[] registers.

Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Tested-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Acked-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>