mpc85xx: switch to 3.8

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35871 3c298f89-4303-0410-b956-a3cf2f4a3e73
mpc85xx: remove 3.7 support

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35872 3c298f89-4303-0410-b956-a3cf2f4a3e73