openssl: revert disallowing parallel build

Openssl 1.1.0 made wholesale changes to its building system.
Apparently, parallel builds are working now.

Signed-off-by: Eneas U de Queiroz <cote2004-github@yahoo.com>

package/libs/openssl/Makefile

@@ -15,7 +15,7 @@ PKG_RELEASE:=3
 PKG_USE_MIPS16:=0
 ENGINES_DIR=engines-1.1
 
-PKG_BUILD_PARALLEL:=0
+PKG_BUILD_PARALLEL:=1
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:= \