MIPS: Get rid of duplicate cpu_idle() prototype.

Since 2.6.11-rc1 there is a prototype in <linux/smp.h>.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/smp.c

@@ -32,6 +32,7 @@
 #include <linux/cpumask.h>
 #include <linux/cpu.h>
 #include <linux/err.h>
+#include <linux/smp.h>
 
 #include <asm/atomic.h>
 #include <asm/cpu.h>
@@ -49,8 +50,6 @@ volatile cpumask_t cpu_callin_map;	/* Bitmask of started secondaries */
 int __cpu_number_map[NR_CPUS];		/* Map physical to logical */
 int __cpu_logical_map[NR_CPUS];		/* Map logical to physical */
 
-extern void cpu_idle(void);
-
 /* Number of TCs (or siblings in Intel speak) per CPU core */
 int smp_num_siblings = 1;
 EXPORT_SYMBOL(smp_num_siblings);