Conditionally declare suspend_data on CONFIG_PM to avoid
the following warning when CONFIG_OM is not enabled:

drivers/platform/x86/tc1100-wmi.c:55:27: warning:
  'suspend_data' defined but not used [-Wunused-variable]

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>