sparc:cleanup unused code in smp_32.h

After genirq and generic clockevent support at sparc32,
smp4m_irq_rotate(), prof_multiplier() and prof_counter()
are no longer used and should be removed.

Find more info from commit 6baa9b20 & 62f08283.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>