s390: simplify disabled_wait

The disabled_wait() function uses its argument as the PSW address when
it stops the CPU with a wait PSW that is disabled for interrupts.
The different callers sometimes use a specific number like 0xdeadbeef
to indicate a specific failure, the early boot code uses 0 and some
other calls sites use __builtin_return_address(0).

At the time a dump is created the current PSW and the registers of a
CPU are written to lowcore to make them avaiable to the dump analysis
tool. For a CPU stopped with disabled_wait the PSW and the registers
do not really make sense together, the PSW address does not point to
the function the registers belong to.

Simplify disabled_wait() by using _THIS_IP_ for the PSW address and
drop the argument to the function.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

kernel/panic.c

@@ -318,12 +318,7 @@ void panic(const char *fmt, ...)
 	}
 #endif
 #if defined(CONFIG_S390)
-	{
-		unsigned long caller;
-
-		caller = (unsigned long)__builtin_return_address(0);
-		disabled_wait(caller);
-	}
+	disabled_wait();
 #endif
 	pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
 	local_irq_enable();