drivers/thermal/thermal_sys.c: fix build warning

With CONFIG_NET=n:

drivers/thermal/thermal_sys.c:63: warning: 'thermal_event_seqnum' defined but not used

Move 'thermal_event_seqnum' definition inside the '#ifdef CONFIG_NET'

[akpm@linux-foundation.org: make thermal_event_seqnum local to generate_netlink_event()]
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>
Acked-by: Durgadoss R <durgadoss.r@intel.com>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>