sparc32: fix sparse warnings in sun4d_irq.c

Fix following warnings:
sun4d_irq.c:146:6: warning: symbol 'sun4d_handler_irq' was not declared. Should it be static?
sun4d_irq.c:239:17: warning: symbol 'sun4d_irq' was not declared. Should it be static?
sun4d_irq.c:288:14: warning: symbol '_sun4d_build_device_irq' was not declared. Should it be static?
sun4d_irq.c:323:14: warning: symbol 'sun4d_build_device_irq' was not declared. Should it be static?
sun4d_irq.c:386:14: warning: symbol 'sun4d_build_timer_irq' was not declared. Should it be static?
sun4d_irq.c:482:13: warning: symbol 'sun4d_init_sbi_irq' was not declared. Should it be static?

Apply static when applicable, otherwise add prototype

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