crypto: drop gcrypt thread initialization code

This is only required on gcrypt < 1.6.0, and is thus obsolete
since

  commit b33a84632a
  Author: Daniel P. Berrangé <berrange@redhat.com>
  Date:   Fri May 14 13:04:08 2021 +0100

    crypto: bump min gcrypt to 1.8.0, dropping RHEL-7 support

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

crypto/init.c

@@ -35,21 +35,6 @@
 #include "crypto/random.h"
 
 /* #define DEBUG_GNUTLS */
-
-/*
- * We need to init gcrypt threading if
- *
- *   - gcrypt < 1.6.0
- *
- */
-
-#if (defined(CONFIG_GCRYPT) &&                  \
-     (GCRYPT_VERSION_NUMBER < 0x010600))
-#define QCRYPTO_INIT_GCRYPT_THREADS
-#else
-#undef QCRYPTO_INIT_GCRYPT_THREADS
-#endif
-
 #ifdef DEBUG_GNUTLS
 static void qcrypto_gnutls_log(int level, const char *str)
 {
@@ -57,55 +42,8 @@ static void qcrypto_gnutls_log(int level, const char *str)
 }
 #endif
 
-#ifdef QCRYPTO_INIT_GCRYPT_THREADS
-static int qcrypto_gcrypt_mutex_init(void **priv)
-{                                                                             \
-    QemuMutex *lock = NULL;
-    lock = g_new0(QemuMutex, 1);
-    qemu_mutex_init(lock);
-    *priv = lock;
-    return 0;
-}
-
-static int qcrypto_gcrypt_mutex_destroy(void **priv)
-{
-    QemuMutex *lock = *priv;
-    qemu_mutex_destroy(lock);
-    g_free(lock);
-    return 0;
-}
-
-static int qcrypto_gcrypt_mutex_lock(void **priv)
-{
-    QemuMutex *lock = *priv;
-    qemu_mutex_lock(lock);
-    return 0;
-}
-
-static int qcrypto_gcrypt_mutex_unlock(void **priv)
-{
-    QemuMutex *lock = *priv;
-    qemu_mutex_unlock(lock);
-    return 0;
-}
-
-static struct gcry_thread_cbs qcrypto_gcrypt_thread_impl = {
-    (GCRY_THREAD_OPTION_PTHREAD | (GCRY_THREAD_OPTION_VERSION << 8)),
-    NULL,
-    qcrypto_gcrypt_mutex_init,
-    qcrypto_gcrypt_mutex_destroy,
-    qcrypto_gcrypt_mutex_lock,
-    qcrypto_gcrypt_mutex_unlock,
-    NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL
-};
-#endif /* QCRYPTO_INIT_GCRYPT */
-
 int qcrypto_init(Error **errp)
 {
-#ifdef QCRYPTO_INIT_GCRYPT_THREADS
-    gcry_control(GCRYCTL_SET_THREAD_CBS, &qcrypto_gcrypt_thread_impl);
-#endif /* QCRYPTO_INIT_GCRYPT_THREADS */
-
 #ifdef CONFIG_GNUTLS
     int ret;
     ret = gnutls_global_init();