cpu: Drop "extern" from function declarations in cpuhplock.h

This file was created with a direct cut and paste from cpu.h so
kept the legacy declaration style.

But the Linux coding standard for function declarations in header
files is to avoid use of "extern".

Drop "extern" from all function declarations.
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240610003927.341707-3-tony.luck@intel.com

include/linux/cpuhplock.h

@@ -15,18 +15,18 @@ struct device;
 extern int lockdep_is_cpus_held(void);
 
 #ifdef CONFIG_HOTPLUG_CPU
-extern void cpus_write_lock(void);
-extern void cpus_write_unlock(void);
-extern void cpus_read_lock(void);
-extern void cpus_read_unlock(void);
-extern int  cpus_read_trylock(void);
-extern void lockdep_assert_cpus_held(void);
-extern void cpu_hotplug_disable(void);
-extern void cpu_hotplug_enable(void);
+void cpus_write_lock(void);
+void cpus_write_unlock(void);
+void cpus_read_lock(void);
+void cpus_read_unlock(void);
+int  cpus_read_trylock(void);
+void lockdep_assert_cpus_held(void);
+void cpu_hotplug_disable(void);
+void cpu_hotplug_enable(void);
 void clear_tasks_mm_cpumask(int cpu);
 int remove_cpu(unsigned int cpu);
 int cpu_device_down(struct device *dev);
-extern void smp_shutdown_nonboot_cpus(unsigned int primary_cpu);
+void smp_shutdown_nonboot_cpus(unsigned int primary_cpu);
 
 #else /* CONFIG_HOTPLUG_CPU */