package/libssh2: fix build with libressl >= 3.5.0

Fix the following build failure with libressl raised since bump to
version 3.5.2 in commit 8b216927db080b38fdbf1f8b025b6f90a89d4bc2:

crypt.c:71:25: error: field 'h' has incomplete type
   71 |     _libssh2_cipher_ctx h;
      |                         ^

Fixes:
 - http://autobuild.buildroot.org/results/47f492ccd4888fe4a150b36e12c88f1e068d46b6

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/libssh2/0001-Opaque-structs-in-LibreSSL-3-5.patch

@@ -0,0 +1,27 @@
+From 7f55a033e5054529e5e69f06725dd02a573329b6 Mon Sep 17 00:00:00 2001
+From: Charlie Li <git@vishwin.info>
+Date: Wed, 2 Mar 2022 19:50:56 -0500
+Subject: [PATCH] Opaque structs in LibreSSL 3.5
+
+[Retrieved (and backported) from:
+https://github.com/libssh2/libssh2/pull/682/commits/7f55a033e5054529e5e69f06725dd02a573329b6]
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ src/openssl.h | 5 +++--
+ 1 file changed, 3 insertions(+), 2 deletions(-)
+
+diff --git a/src/openssl.h b/src/openssl.h
+index 3eef02368..c13542481 100644
+--- a/src/openssl.h
++++ b/src/openssl.h
+@@ -94,8 +94,8 @@
+ #include <openssl/pem.h>
+ #include <openssl/rand.h>
+ 
+-#if OPENSSL_VERSION_NUMBER >= 0x10100000L && \
+-    !defined(LIBRESSL_VERSION_NUMBER)
++#if (OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)) || \
++    (defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER >= 0x30500000L)
+ # define HAVE_OPAQUE_STRUCTS 1
+ #endif
+