VMS: Compensate for x86_64 cross compiler type incompatibility

VMS: Compensate for x86_64 cross compiler type incompatibility

The x86_64 cross compiler says that 'unsigned long long' isn't the
same as 'unsigned __int64'.  Sure, and considering that
providers/implementations/rands/seeding/rand_vms.c is specific VMS
only code, it's easy to just change the type to the exact same as
what's specified in the system headers.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16497)