usermodehelper: Tidy up waiting

Rather than using a tri-state integer for the wait flag in
call_usermodehelper_exec, define a proper enum, and use that.  I've
preserved the integer values so that any callers I've missed should
still work OK.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Andi Kleen <ak@suse.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Joel Becker <joel.becker@oracle.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: David Howells <dhowells@redhat.com>
diff --git a/drivers/macintosh/therm_pm72.c b/drivers/macintosh/therm_pm72.c
index dbb2240..3d90fc0 100644
--- a/drivers/macintosh/therm_pm72.c
+++ b/drivers/macintosh/therm_pm72.c
@@ -1770,7 +1770,8 @@
 				"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
 				NULL };
 
-	return call_usermodehelper(critical_overtemp_path, argv, envp, 0);
+	return call_usermodehelper(critical_overtemp_path,
+				   argv, envp, UMH_WAIT_EXEC);
 }