bug: Let report_bug_entry() provide the correct bugaddr

report_bug_entry() always provides zero for bugaddr but could easily
extract the correct address from the provided bug_entry. Just do that to
have proper warning messages.

E.g. adding an artificial:

void foo(void) { WARN_ONCE(1, "bar"); }

function generates this warning message:

WARNING: arch/s390/kernel/setup.c:1017 at 0x0, CPU#0: swapper/0/0
^^^

With the correct bug address this changes to:

WARNING: arch/s390/kernel/setup.c:1017 at foo+0x1c/0x40, CPU#0: swapper/0/0
^^^^^^^^^^^^^

Fixes: 7d2c27a0ec5e ("bug: Add report_bug_entry()")
Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

lib/bug.c

···
 	bool rcu = false;
 
 	rcu = warn_rcu_enter();
-	ret = __report_bug(bug, 0, regs);
+	ret = __report_bug(bug, bug_addr(bug), regs);
 	warn_rcu_exit(rcu);
 
 	return ret;