Fix return value.

Instead of wrongfully always returning OK, return the real error code.

This was uncovered by the amalgamation via the warning:

```
pre_gen/tomcrypt_amalgam.c: In function ‘der_decode_custom_type_ex’:
pre_gen/tomcrypt_amalgam.c:49820:10: warning: ‘*(unsigned int *)((char *)&ident + offsetof(ltc_asn1_list, type))’ may be used uninitialized [-Wmaybe-uninitialized]
49820 |       if ((ident.type != root->type) ||
      |          ^
pre_gen/tomcrypt_amalgam.c:49780:18: note: ‘*(unsigned int *)((char *)&ident + offsetof(ltc_asn1_list, type))’ was declared here
49780 |    ltc_asn1_list ident;
      |                  ^~~~~
```

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

src/pk/asn1/der/general/der_decode_asn1_identifier.c

@@ -117,7 +117,7 @@ int der_decode_asn1_identifier(const unsigned char *in, unsigned long *inlen, lt
       }
    }
 
-   return CRYPT_OK;
+   return err;
 }
 
 #endif