platform/x86: thinkpad_acpi: initialize tp_nvram_state variable

clang static analysis flags this represenative problem
thinkpad_acpi.c:2523:7: warning: Branch condition evaluates
  to a garbage value
                if (!oldn->mute ||
                    ^~~~~~~~~~~

In hotkey_kthread() mute is conditionally set by hotkey_read_nvram()
but unconditionally checked by hotkey_compare_and_issue_event().
So the tp_nvram_state variable s[2] needs to be initialized.

Fixes: 01e88f25 ("ACPI: thinkpad-acpi: add CMOS NVRAM polling for hot keys (v9)")
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: mark gross <mgross@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/thinkpad_acpi.c

@@ -2569,7 +2569,7 @@ static void hotkey_compare_and_issue_event(struct tp_nvram_state *oldn,
  */
 static int hotkey_kthread(void *data)
 {
-	struct tp_nvram_state s[2];
+	struct tp_nvram_state s[2] = { 0 };
 	u32 poll_mask, event_mask;
 	unsigned int si, so;
 	unsigned long t;