Modify the add_seeds_stringlist() macro to fix a preprocessor error

Modify the add_seeds_stringlist() macro to fix a preprocessor error

When OpenSSL is configured using `--with-rand-seed=devrandom`, the preprocessor
reports the following error

    crypto/info.c:104:66: error:
            macro "add_seeds_stringlist" passed 3 arguments, but takes just 2
            add_seeds_stringlist("random-device", { DEVRANDOM, NULL });

The reason why the preprocessor complains about three arguments being passed
is that according to [1], balanced braces in macro arguments don't prevent the
comma from acting as an argument separator:

    3.3 Macro Arguments
    ...
    Parentheses within each argument must balance;
    a comma within such parentheses does not end the argument.
    However, there is no requirement for square brackets or braces to balance,
    and they do not prevent a comma from separating arguments.

Also introduced an iteration pointer `p`, because `dev` is not an lvalue:

    crypto/info.c:78:41: error:
            lvalue required as increment operand
            for (; *dev != NULL; dev++) {

[1] https://gcc.gnu.org/onlinedocs/cpp/Macro-Arguments.html

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/10762)