qemu: add libssh2 optional dependency

Make sure that qemu uses libssh2 when libssh2 is enabled, for build
consistency.

Cc: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit d769377a41e172e1963351c168c97a1212561133)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/qemu/qemu.mk

@@ -212,6 +212,13 @@ else
 QEMU_OPTS += --disable-tools
 endif
 
+ifeq ($(BR2_PACKAGE_LIBSSH2),y)
+QEMU_OPTS += --enable-libssh2
+QEMU_DEPENDENCIES += libssh2
+else
+QEMU_OPTS += --disable-libssh2
+endif
+
 # Override CPP, as it expects to be able to call it like it'd
 # call the compiler.
 define QEMU_CONFIGURE_CMDS