kernel: ensure that the arm exception handlers get preserved

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35937 3c298f89-4303-0410-b956-a3cf2f4a3e73
kernel: prevent -f*-sections from leaking into the boot zImage wrapper on arm

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35938 3c298f89-4303-0410-b956-a3cf2f4a3e73