module: enable automatic module signing with FIPS 202 SHA-3

Add Kconfig options to use SHA-3 for kernel module signing. 256 size
for RSA only, and higher sizes for RSA and NIST P-384.

Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>