tools, config.mk: add binutils-version

Modeled after gcc-version, add function to get binutils version.

Signed-off-by: Allen Martin <amartin@nvidia.com>
Acked-by: Wolfgang Denk <wd@denx.de>
diff --git a/config.mk b/config.mk
index c3822a2..51b4783 100644
--- a/config.mk
+++ b/config.mk
@@ -128,6 +128,7 @@
 # cc-version
 # Usage gcc-ver := $(call cc-version)
 cc-version = $(shell $(SHELL) $(SRCTREE)/tools/gcc-version.sh $(CC))
+binutils-version = $(shell $(SHELL) $(SRCTREE)/tools/binutils-version.sh $(AS))
 
 #
 # Include the make variables (CC, etc...)