crypto: api - Export crypto_boot_test_finished

We need to export crypto_boot_test_finished in case api.c is
built-in while algapi.c is built as a module.

Fixes: adad556e

 ("crypto: api - Fix built-in testing dependency failures")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Stephen Rothwell <sfr@canb.auug.org.au> # ppc32 build
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>