perf: Fix get_recursion_context()

One should use in_serving_softirq() to detect SoftIRQ context.

Fixes: 96f6d4444302 ("perf_counter: avoid recursion")
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]

kernel/events/internal.h

···
 		rctx = 3;
 	else if (in_irq())
 		rctx = 2;
-	else if (in_softirq())
+	else if (in_serving_softirq())
 		rctx = 1;
 	else
 		rctx = 0;