sched: Always inline is_percpu_thread()

  vmlinux.o: warning: objtool: check_preemption_disabled()+0x81: call to is_percpu_thread() leaves .noinstr.text section

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928084218.063371959@infradead.org

include/linux/sched.h

@@ -1720,7 +1720,7 @@ extern struct pid *cad_pid;
 #define tsk_used_math(p)			((p)->flags & PF_USED_MATH)
 #define used_math()				tsk_used_math(current)
 
-static inline bool is_percpu_thread(void)
+static __always_inline bool is_percpu_thread(void)
 {
 #ifdef CONFIG_SMP
 	return (current->flags & PF_NO_SETAFFINITY) &&