linux-next for 4.6-rc1 timeline reported ARC build failures !THP

| arch/arc/include/asm/tlbflush.h:29:0: warning: "flush_pmd_tlb_range" redefined [enabled by default]
| arch/arc/include/asm/tlbflush.h:29:0: warning: "flush_pmd_tlb_range" redefined [enabled by default]
| arch/arc/include/asm/tlbflush.h:29:0: warning: "flush_pmd_tlb_range" redefined [enabled by default]

Turns out that commit ("mm/thp/migration: switch from flush_tlb_range
to flush_pmd_tlb_range") triggered the issue while the problem was in
ARC code where THP specific helpers were not guarded with #ifdef.
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

- Add mm_cpumask setting (aggregating only, unlike some other arches)
  used to restrict the TLB flush cross-calling

- cross-calling versions of TLB flush routines (thanks to Noam)
Signed-off-by: NNoam Camus <noamc@ezchip.com>
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

Signed-off-by: NVineet Gupta <vgupta@synopsys.com>