cpumask: update cpumask_next_wrap() signature

The extern specifier is not needed for this declaration, so drop it.  The
function also depends only on the input parameters, and has no side
effects, so it can be marked __pure like other functions in cpumask.h.

Link: https://lkml.kernel.org/r/72ab755695b74bb5fbaa756ae4c0edd708d172f1.1656777646.git.sander@svanheule.netSigned-off-by: Sander Vanheule <sander@svanheule.net>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Marco Elver <elver@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/cpumask.h

@@ -229,7 +229,7 @@ int cpumask_any_distribute(const struct cpumask *srcp);
 		(cpu) = cpumask_next_zero((cpu), (mask)),	\
 		(cpu) < nr_cpu_ids;)
 
-extern int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap);
+int __pure cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap);
 
 /**
  * for_each_cpu_wrap - iterate over every cpu in a mask, starting at a specified location