arm: make return_address available for ARM_UNWIND
This fixes a warning saying:

    warning: #warning "TODO: return_address should use unwind tables"

And, this enables return_address using unwind information. If ARM_UNWIND is
selected, unwind_frame in unwind.c will be called in walk_stackframe.

Signed-off-by: sahara <keun-o.park@windriver.com>
mm: slub: fix 'x' uninitialized in ‘show_slab_objects’
kernel: futex: fix unused variable 'curval2' in ‘futex_requeue’
drivers/usb/gadget/f_qdss.c: gcc 4.8 fixup

Signed-off-by: Paul Reioux <reioux@gmail.com>