PM: Add missing syscore_suspend() and syscore_resume() calls

Device suspend/resume infrastructure is used not only by the suspend
and hibernate code in kernel/power, but also by APM, Xen and the
kexec jump feature.  However, commit 40dc166cb5
(PM / Core: Introduce struct syscore_ops for core subsystems PM)
failed to add syscore_suspend() and syscore_resume() calls to that
code, which generally leads to breakage when the features in question
are used.

To fix this problem, add the missing syscore_suspend() and
syscore_resume() calls to arch/x86/kernel/apm_32.c, kernel/kexec.c
and drivers/xen/manage.c.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

drivers/base/syscore.c

@@ -73,6 +73,7 @@ int syscore_suspend(void)
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(syscore_suspend);
 
 /**
  * syscore_resume - Execute all the registered system core resume callbacks.
@@ -95,6 +96,7 @@ void syscore_resume(void)
 				"Interrupts enabled after %pF\n", ops->resume);
 		}
 }
+EXPORT_SYMBOL_GPL(syscore_resume);
 #endif /* CONFIG_PM_SLEEP */
 
 /**