amd64-microcode: create early load microcode image

Create initrd image with packed microcode. This'll allow to load it at
early boot stage.

Signed-off-by: Tomasz Maciej Nowak <tomek_n@o2.pl>

package/firmware/amd64-microcode/Makefile

@@ -35,11 +35,17 @@ define Build/Prepare
 endef
 
 define Build/Compile
+	mkdir -p $(PKG_BUILD_DIR)/kernel/x86/microcode/
+	cat $(PKG_BUILD_DIR)/microcode_amd*.bin \
+		> $(PKG_BUILD_DIR)/kernel/x86/microcode/AuthenticAMD.bin
+	(cd $(PKG_BUILD_DIR); \
+	echo "kernel/x86/microcode/AuthenticAMD.bin" \
+		| cpio -o -H newc --reproducible > amd-ucode.cpio)
 endef
 
 define Package/amd64-microcode/install
-	$(INSTALL_DIR) $(1)/lib/firmware/amd-ucode
-	$(INSTALL_DATA) $(PKG_BUILD_DIR)/*.bin $(1)/lib/firmware/amd-ucode
+	$(INSTALL_DIR) $(1)/boot
+	$(INSTALL_DATA) $(PKG_BUILD_DIR)/amd-ucode.cpio $(1)/boot/amd-ucode.img
 endef
 
 $(eval $(call BuildPackage,amd64-microcode))