UBUNTU: [Config] Disble stack protector for powerpc-smp

UBUNTU: [Config] Disble stack protector for powerpc-smp

Fixes FTBFS:

 arch/powerpc/platforms/built-in.o: In function `bootx_add_display_props':
 /<<PKGBUILDDIR>>/arch/powerpc/platforms/powermac/bootx_init.c:211: undefined reference to `__stack_chk_fail_local'
 arch/powerpc/platforms/built-in.o: In function `bootx_scan_dt_build_struct':
 /<<PKGBUILDDIR>>/arch/powerpc/platforms/powermac/bootx_init.c:350: undefined reference to `__stack_chk_fail_local'
 arch/powerpc/platforms/built-in.o: In function `bootx_init':
 /<<PKGBUILDDIR>>/arch/powerpc/platforms/powermac/bootx_init.c:596: undefined reference to `__stack_chk_fail_local'
 ld: .tmp_vmlinux1: hidden symbol `__stack_chk_fail_local' isn't defined
 ld: final link failed: Bad value

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>