sh: Build fix: define more __movmem* symbols

ERROR: "__movmemSI12" [net/unix/unix.ko] undefined!
ERROR: "__movmemSI52" [net/ipv6/sit.ko] undefined!
ERROR: "__movmemSI24" [net/ipv6/ipv6.ko] undefined!
ERROR: "__movmemSI60" [net/ipv6/ipv6.ko] undefined!
ERROR: "__movmemSI16" [net/ipv6/ipv6.ko] undefined!
ERROR: "__movmemSI20" [net/ipv6/ipv6.ko] undefined!
ERROR: "__movmemSI32" [net/ipv6/ipv6.ko] undefined!

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>