driver/intel/wifi: Update wifi wake source in elog

In S3 resume, wifi is one of the wake sources.

If elog is enabled in config, then log wifi wakes in elog.

BUG=b:36992859
TEST= Build for Soraka. Do WoWlan during S3. Verify elog having update
on wake due to Wifi.

Change-Id: I7d42c5c81e0a3f7a3f94c3f6b7d2ebdf029d1aff
Signed-off-by: Naresh G Solanki <naresh.solanki@intel.com>
Reviewed-on: https://review.coreboot.org/20455
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/include/elog.h

@@ -149,6 +149,7 @@
 #define  ELOG_WAKE_SOURCE_PME_XDCI         0x1c
 #define  ELOG_WAKE_SOURCE_PME_XHCI_USB_2   0x1d
 #define  ELOG_WAKE_SOURCE_PME_XHCI_USB_3   0x1e
+#define  ELOG_WAKE_SOURCE_PME_WIFI         0x1f
 
 struct elog_event_data_wake {
 	u8 source;