powerpc/eeh: Fix build with STACKTRACE=n

The build breaks when STACKTRACE=n, eg. skiroot_defconfig:

  arch/powerpc/kernel/eeh_event.c:124:23: error: implicit declaration of function 'stack_trace_save'

Fix it with some ifdefs for now.

Fixes: 25baf3d816 ("powerpc/eeh: Defer printing stack trace")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/eeh.h

@@ -89,6 +89,7 @@ struct eeh_pe {
 	struct list_head child;		/* Memb. child_list/eeh_phb_pe	*/
 	struct list_head edevs;		/* List of eeh_dev in this PE	*/
 
+#ifdef CONFIG_STACKTRACE
 	/*
 	 * Saved stack trace. When we find a PE freeze in eeh_dev_check_failure
 	 * the stack trace is saved here so we can print it in the recovery
@@ -99,6 +100,7 @@ struct eeh_pe {
 	 */
 	unsigned long stack_trace[64];
 	int trace_entries;
+#endif /* CONFIG_STACKTRACE */
 };
 
 #define eeh_pe_for_each_dev(pe, edev, tmp) \

arch/powerpc/kernel/eeh_driver.c

@@ -908,6 +908,7 @@ void eeh_handle_normal_event(struct eeh_pe *pe)
 		       eeh_pe_loc_get(pe), eeh_pe_loc_get(phb_pe));
 	}
 
+#ifdef CONFIG_STACKTRACE
 	/*
 	 * Print the saved stack trace now that we've verified there's
 	 * something to recover.
@@ -926,7 +927,7 @@ void eeh_handle_normal_event(struct eeh_pe *pe)
 
 		pe->trace_entries = 0;
 	}
-
+#endif /* CONFIG_STACKTRACE */
 
 	eeh_pe_update_time_stamp(pe);
 	pe->freeze_count++;

arch/powerpc/kernel/eeh_event.c

@@ -117,12 +117,14 @@ int __eeh_send_failure_event(struct eeh_pe *pe)
 	 * while the PE is sitting in the event queue.
 	 */
 	if (pe) {
+#ifdef CONFIG_STACKTRACE
 		/*
 		 * Save the current stack trace so we can dump it from the
 		 * event handler thread.
 		 */
 		pe->trace_entries = stack_trace_save(pe->stack_trace,
 					 ARRAY_SIZE(pe->stack_trace), 0);
+#endif /* CONFIG_STACKTRACE */
 
 		eeh_pe_state_mark(pe, EEH_PE_RECOVERING);
 	}