urandom-seed: update Makefile

- update SPDX license identifier
- use https in URL
- use default PKG_BUILD_DIR

Suggested-by: Josef Schlehofer <josef.schlehofer@nic.cz>
Tested-by: Josef Schlehofer <josef.schlehofer@nic.cz>
Signed-off-by: Sungbo Eo <mans0n@gorani.run>

package/system/urandom-seed/Makefile

@@ -2,10 +2,8 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=urandom-seed
 PKG_VERSION:=1.0
-PKG_RELEASE:=1
-PKG_LICENSE:=GPL-2.0
-
-PKG_BUILD_DIR := $(BUILD_DIR)/$(PKG_NAME)
+PKG_RELEASE:=2
+PKG_LICENSE:=GPL-2.0-only
 
 include $(INCLUDE_DIR)/package.mk
 
@@ -14,7 +12,7 @@ define Package/urandom-seed
   CATEGORY:=Base system
   DEPENDS:=+getrandom
   TITLE:=/etc/urandom.seed handling for OpenWrt
-  URL:=http://openwrt.org/
+  URL:=https://openwrt.org/
 endef
 
 define Build/Prepare