crypto: api - Move module sig ifdef into accessor function

Currently we're hiding mod->sig_ok under an ifdef in open code.
This patch adds a module_sig_ok accessor function and removes that
ifdef.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>

diff --cc crypto/algapi.c
Simple merge

diff --cc include/linux/module.h
Simple merge