[SPARC64]: Fix some Niagara memcpy() bugs.

We need to restore the %asi register properly.
For the kernel this means get_fs(), for user this
means ASI_PNF.

Also, NGcopy_to_user.S was including U3memcpy.S instead
of NGmemcpy.S, oops :-)

Signed-off-by: David S. Miller <davem@davemloft.net>