ACPI: thinkpad-acpi: fix hotkey_get_tablet_mode

I used the wrong return convention on hotkey_get_tablet_mode(), breaking a lot
of stuff.  Bad Henrique!

Fix it to return the status in the parameter-by-reference, and IO status on
the function return value.  Duh.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: Zdenek Kabelac <zdenek.kabelac@gmail.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Lukas Hejtmanek <xhejtman@ics.muni.cz>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/misc/thinkpad_acpi.c

diff --git a/drivers/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
index bb269d0..6cb7812 100644
--- a/drivers/misc/thinkpad_acpi.c
+++ b/drivers/misc/thinkpad_acpi.c
@@ -1078,7 +1078,8 @@
 	if (!acpi_evalf(hkey_handle, &s, "MHKG", "d"))
 		return -EIO;
 
-	return ((s & TP_HOTKEY_TABLET_MASK) != 0);
+	*status = ((s & TP_HOTKEY_TABLET_MASK) != 0);
+	return 0;
 }
 
 /*