ACPI Thinkpad: We must always call va_end() after va_start() but do not do so in thinkpad_acpi.c::acpi_evalf()

Hi,

In drivers/platform/x86/thinkpad_acpi.c::acpi_evalf() we don't always call
va_end() after va_start(). This patch corrects that.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Acked-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Matthew Garrett <mjg@redhat.com>
diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index f372dc7..a974ca3 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -589,6 +589,7 @@
 		default:
 			printk(TPACPI_ERR "acpi_evalf() called "
 			       "with invalid format character '%c'\n", c);
+			va_end(ap);
 			return 0;
 		}
 	}