Latest busybox version cannot be used

busybox sha1 76915bf7 (2015-12-19) makes use of MTD_FILE_MODE_RAW.
This is correctly defined in linux/include/uapi/mtd/mtd-abi.h, but
unfortunately not in the toolchain headers
<toolchain>/arm-linux-gnueabihf/libc/usr/include/mtd/mtd-abi.h

Hence the previous sha1 is to be used, that is dbf5a6da

Change-Id: Iec81120623161349cbe2c35601b112d4235f60dc
Reviewed-by: Joakim Bech <joakim.bech@linaro.org>
Tested-by: Pascal Brand <pascal.brand@linaro.org> (QEMU)
Signed-off-by: Pascal Brand <pascal.brand@st.com>
diff --git a/hikey.xml b/hikey.xml
index 14b5066..82540cb 100644
--- a/hikey.xml
+++ b/hikey.xml
@@ -26,7 +26,7 @@
 	<project path="optee_test" name="optee_test" />
 
 	<!-- busybox -->
-	<project remote="busybox" path="busybox" name="busybox" />
+	<project remote="busybox" path="busybox" name="busybox" revision="dbf5a6da6a4295ce26edd1ce34fde567d19afa02" />
 
 	<!-- ARM gits -->
 	<!-- project remote="arm" path="arm-trusted-firmware" name="arm-trusted-firmware" /-->