crypto: api - Add crypto_alloc_instance2

This patch adds a new argument to crypto_alloc_instance which
sets aside some space before the instance for use by algorithms
such as shash that place type-specific data before crypto_alg.

For compatibility the function has been renamed so that existing
users aren't affected.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --cc crypto/algapi.c
Simple merge

diff --cc include/crypto/algapi.h
Simple merge