arch/sparc: Rename exception handlers

Rename exception handlers to memcpy_xxx as these
are going to be used by new memcpy routines and these
handlers are not exclusive to NG4memcpy anymore.

Signed-off-by: Babu Moger <babu.moger@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>