cryptenroll: allow to use a public key on a token

This patch allows systemd-cryptenroll to enroll directly with a public key if a certificate is missing on a token.

Fixes: #30675

src/basic/memory-util.h

@@ -107,3 +107,6 @@ static inline void erase_and_freep(void *p) {
 static inline void erase_char(char *p) {
         explicit_bzero_safe(p, sizeof(char));
 }
+
+/* Makes a copy of the buffer with reversed order of bytes */
+void *memdup_reverse(const void *mem, size_t size);