[PATCH V4] powerpc: Implement {cmp}xchg for u8 and u16

[Peter Zijlstra]

On Wed, Apr 27, 2016 at 05:16:45PM +0800, Pan Xinhui wrote:
> From: Pan Xinhui <xinhui.pan at linux.vnet.ibm.com>
> 
> Implement xchg{u8,u16}{local,relaxed}, and
> cmpxchg{u8,u16}{,local,acquire,relaxed}.
> 
> It works on all ppc.
> 
> remove volatile of first parameter in __cmpxchg_local and __cmpxchg
> 
> Suggested-by: Peter Zijlstra (Intel) <peterz at infradead.org>
> Signed-off-by: Pan Xinhui <xinhui.pan at linux.vnet.ibm.com>

Generally has the right shape; and I trust others to double check the
ppc-asm minutia.

Acked-by: Peter Zijlstra (Intel) <peterz at infradead.org>