crypto: n2 - Silence gcc format-truncation false positive warnings

The heuristics used by gcc triggers false positive truncation
warnings in hifn_alg_alloc.

Add checks on snprintf calls to silence these warnings, including
the one for cra_driver_name even though it does not currently trigger
a gcc warning.

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