thinkpad_acpi.c: Fix sparse warning (make undeclared var static)

Fix the following sparse warning:

thinkpad_acpi.c:3459:11: warning: symbol 'adaptive_keyboard_modes' was not declared. Should it be static?
Signed-off-by: NLad, Prabhakar <prabhakar.csengg@gmail.com>
Acked-by: NHenrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: NDarren Hart <dvhart@linux.intel.com>

drivers/platform/x86/thinkpad_acpi.c

@@ -3456,7 +3456,7 @@ enum ADAPTIVE_KEY_MODE {
 	LAYFLAT_MODE
 };
 
-const int adaptive_keyboard_modes[] = {
+static const int adaptive_keyboard_modes[] = {
 	HOME_MODE,
 /*	WEB_BROWSER_MODE = 2,
 	WEB_CONFERENCE_MODE = 3, */