poky: add fedora-25 to the SANITY_TESTED_DISTROS

I have tested Fedora 25 enough times to add it to the tested distros
list. Additionally, in Guadalajara's staging autobuilder has been
tested for some time now so it is safe to put it in.

(From meta-yocto rev: c6ac52f061207e8fcedebda0ca4279fa5b07b9a6)

Signed-off-by: Benjamin Esquivel <benjamin.esquivel@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-poky/conf/distro/poky.conf

@@ -83,6 +83,7 @@ SANITY_TESTED_DISTROS ?= " \
             fedora-22 \n \
             fedora-23 \n \
             fedora-24 \n \
+            fedora-25 \n \
             centos-7 \n \
             debian-8 \n \
             opensuse-13.2 \n \