xtensa: add SMP support

This is largely based on SMP code from the xtensa-2.6.29-smp tree by
Piet Delaney, Marc Gauthier, Joe Taylor, Christian Zankel (and possibly
other Tensilica folks).

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

diff --cc arch/xtensa/Kconfig
Simple merge

diff --cc arch/xtensa/include/asm/barrier.h
Simple merge

diff --cc arch/xtensa/include/asm/bitops.h
Simple merge

diff --cc arch/xtensa/include/asm/cacheflush.h
Simple merge

diff --cc arch/xtensa/include/asm/mmu.h
Simple merge

diff --cc arch/xtensa/include/asm/mmu_context.h
Simple merge

diff --cc arch/xtensa/include/asm/ptrace.h
Simple merge

diff --cc arch/xtensa/include/asm/smp.h
Simple merge

diff --cc arch/xtensa/include/asm/timex.h
Simple merge

diff --cc arch/xtensa/include/asm/tlbflush.h
Simple merge

diff --cc arch/xtensa/include/asm/traps.h
Simple merge

diff --cc arch/xtensa/kernel/Makefile
Simple merge

diff --cc arch/xtensa/kernel/head.S
Simple merge

diff --cc arch/xtensa/kernel/irq.c
Simple merge

diff --cc arch/xtensa/kernel/mxhead.S
Simple merge

diff --cc arch/xtensa/kernel/setup.c
Simple merge

diff --cc arch/xtensa/kernel/smp.c
Simple merge

diff --cc arch/xtensa/kernel/traps.c
Simple merge

diff --cc arch/xtensa/kernel/vmlinux.lds.S
Simple merge

diff --cc arch/xtensa/mm/cache.c
Simple merge

diff --cc arch/xtensa/mm/fault.c
Simple merge

diff --cc arch/xtensa/mm/mmu.c
Simple merge

diff --cc arch/xtensa/mm/tlb.c
Simple merge

diff --cc arch/xtensa/platforms/xtfpga/include/platform/hardware.h
Simple merge