The heuristics used by gcc triggers false positive truncation
warnings in hifn_alg_alloc.  The warning triggered by the strings
here are clearly false positives (see
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95755).

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>