mpc52xx: add support for 3.8

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

git-svn-id: svn://svn.openwrt.org/openwrt@35975 3c298f89-4303-0410-b956-a3cf2f4a3e73
mpc52xx: switch to 3.8

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

git-svn-id: svn://svn.openwrt.org/openwrt@35976 3c298f89-4303-0410-b956-a3cf2f4a3e73
mpc52xx: remove 3.3 support

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

git-svn-id: svn://svn.openwrt.org/openwrt@35977 3c298f89-4303-0410-b956-a3cf2f4a3e73