ustream-ssl: variants conflict with each other

This adds conflicts between variants of libustream pacakge.
They provide the same file and thus it should not be possible to install
them side by side.

Signed-off-by: Karel Kočí <[email protected]>

package/libs/ustream-ssl/Makefile

@@ -1,7 +1,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=ustream-ssl
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL=$(PROJECT_GIT)/project/ustream-ssl.git
@@ -37,6 +37,7 @@ define Package/libustream-wolfssl
   $(Package/libustream/default)
   TITLE += (wolfssl)
   DEPENDS += +PACKAGE_libustream-wolfssl:libwolfssl
+  CONFLICTS := libustream-openssl
   VARIANT:=wolfssl
 endef
 
@@ -44,6 +45,7 @@ define Package/libustream-mbedtls
   $(Package/libustream/default)
   TITLE += (mbedtls)
   DEPENDS += +libmbedtls
+  CONFLICTS := libustream-openssl libustream-wolfssl
   VARIANT:=mbedtls
   DEFAULT_VARIANT:=1
 endef