MIPS: remove orphan sb1250_time_init() declaration

All uses of sb1250_time_init() have been removed by
commit d527eef5b7f1 ("[MIPS] Sibyte: Finish conversion to modern
time APIs."), so remove the orphan declaration.

The comments about sb1250_time_init() is useless in arch_init_irq(),
so remove these comments.

Signed-off-by: Gaosheng Cui <[e-mail]>
Reviewed-by: Philippe Mathieu-Daudé <[e-mail]>
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

arch/mips/include/asm/sibyte/sb1250.h

···
 extern unsigned int periph_rev;
 extern unsigned int zbbus_mhz;
 
-extern void sb1250_time_init(void);
 extern void sb1250_mask_irq(int cpu, int irq);
 extern void sb1250_unmask_irq(int cpu, int irq);
 

arch/mips/sibyte/sb1250/irq.c

···
 	__raw_writeq(tmp, IOADDR(A_IMR_REGISTER(0, R_IMR_INTERRUPT_MASK)));
 	__raw_writeq(tmp, IOADDR(A_IMR_REGISTER(1, R_IMR_INTERRUPT_MASK)));
 
-	/*
-	 * Note that the timer interrupts are also mapped, but this is
-	 * done in sb1250_time_init().	Also, the profiling driver
-	 * does its own management of IP7.
-	 */
-
 	/* Enable necessary IPs, disable the rest */
 	change_c0_status(ST0_IM, imask);
 }