config/odroidc2: force usage of gcc 4.9.x

due to an issue with odroid's u-boot, compiling u-boot with
gcc 5.x will result in a non booting image.
so a gcc 4.9.x compiler must be used.
this solve bug #9326

thanks to Erico Nunes <nunes.erico@gmail.com> for pointing
to the right issue.

Reported-by: <gahabana@mail.com>
Signed-off-by: Dagg Stompler <daggs@gmx.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/odroidc2_defconfig

@@ -7,6 +7,7 @@ BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_ROOTFS_POST_IMAGE_SCRIPT="board/hardkernel/odroidc2/post-image.sh"
 BR2_PACKAGE_ODROID_SCRIPTS=y
+BR2_GCC_VERSION_4_9_X=y
 
 # Kernel
 BR2_KERNEL_HEADERS_VERSION=y