Add the debian revision to the U-boot version, which is displayed at
boot and can be helpful to determine which specific version is used.

--- a/Makefile
+++ b/Makefile
@@ -447,7 +447,7 @@
 
 # Read UBOOTRELEASE from include/config/uboot.release (if it exists)
 UBOOTRELEASE = $(shell cat include/config/uboot.release 2> /dev/null)
-UBOOTVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
+UBOOTVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)$(DEBIAN_REVISION)
 
 export VERSION PATCHLEVEL SUBLEVEL UBOOTRELEASE UBOOTVERSION
 export ARCH CPU BOARD VENDOR SOC CPUDIR BOARDDIR
