build: add config symbols for different ARM arch levels

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@36620 3c298f89-4303-0410-b956-a3cf2f4a3e73
valgrind: do not depend on a particular ARM target, depend on the arch level

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@36621 3c298f89-4303-0410-b956-a3cf2f4a3e73