sparc: Fix piggyback with newer binutils.

Newer versions of binutils mark '_end' as 'B' instead of 'A' for
whatever reason.

To be honest, the piggyback code doesn't actually care what kind
of symbol _start and _end are, it just wants to find them and
record the address.

So remove the type from the match strings.

Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>