sparc32: fix sparse warnings in sun4m_smp.c

Fix following warnings:
sun4m_smp.c:72:13: warning: symbol 'smp4m_boot_cpus' was not declared. Should it be static?
sun4m_smp.c:78:5: warning: symbol 'smp4m_boot_one_cpu' was not declared. Should it be static?
sun4m_smp.c:120:13: warning: symbol 'smp4m_smp_done' was not declared. Should it be static?
sun4m_smp.c:230:6: warning: symbol 'smp4m_cross_call_irq' was not declared. Should it be static?
sun4m_smp.c:240:6: warning: symbol 'smp4m_percpu_timer_interrupt' was not declared. Should it be static?

Add proper declarations.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>