ravpower-mcu: add missing PKG_RELEASE

This fixes the imagebuilder for this device.

Signed-off-by: David Bauer <[email protected]>

package/utils/ravpower-mcu/Makefile

@@ -1,6 +1,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=ravpower-mcu
+PKG_RELEASE:=1
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL=https://github.com/blocktrron/ravpower-mcu.git