utils/px5g-standalone: drop Build/Prepare rule in favor of default one

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

package/utils/px5g-standalone/Makefile

@@ -27,11 +27,6 @@ define Package/px5g-standalone/description
  and PEM format for use with stunnel, uhttpd and others.
 endef
 
-define Build/Prepare
-	mkdir -p $(PKG_BUILD_DIR)
-	$(CP) ./src/* $(PKG_BUILD_DIR)/
-endef
-
 define Package/px5g-standalone/install
 	$(INSTALL_DIR) $(1)/usr/sbin
 	$(INSTALL_BIN) $(PKG_BUILD_DIR)/px5g $(1)/usr/sbin/px5g