brcm2708-gpu-fw: update to Sep. 27 2014 snapshot

Update the brcm2708-gpu-fw package to commit
e25efc4545d0cef7c49c82e770b3e4ccfc8aba4c

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42676 3c298f89-4303-0410-b956-a3cf2f4a3e73