buildroot

binutils: switch to version 2.25 by default

binutils 2.26 has been released, it is time to switch to 2.25 as the
default version.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>