lib/crypto: support sha384/sha512 in x509/pkcs7

Set digest_size SHA384 and SHA512 algorithms in pkcs7 and x509,
(not set by ported linux code, but needed by __UBOOT__ part).

EFI_CAPSULE_AUTHENTICATE doesn't select these algos but required for
correctness if certificates contain sha384WithRSAEncryption or
sha512WithRSAEncryption OIDs.

Signed-off-by: Dhananjay Phadke <dphadke@linux.microsoft.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>