[PATCH][SPARC] missing membar in niagara2_memcpy

[Jose E. Marchesi]

    > Several system tests of a certain (very data intensive) program crashed
    > as soon as it started to use multilib/niagara2_memcpy, due to memory
    > corruption.  They run just fine after this patch is applied.
    > 
    > We also observed that jar would occasionally raise
    > java.util.zip.ZipException.  This was due to the fact the last two bytes
    > of a buffer were not apparently being copied by memcpy.  Again, this
    > patch fixes that problem.
    > 
    >     The member is extremely expensive and I avoided it intentionally.
    > 
    > Yes I suspected that, given how carefully that code is written.  We are
    > aware that membars are painful on the T2 (any membar, because all
    > flavors are mapped to #Sync) but the risk of overlaps is not only
    > theoretical in this case, unfortunately :(
    
    Ok I'll install this fix after some testing and update the copy of the
    same code in the kernel as well, thanks.

Thanks.