Add support for CONFIG_NO_ROAMING to Makefile

Commit e9af53ad39a19264bf5307a1b5923afc2b2f9b06 introduced new
CONFIG_NO_ROAMING configuration parameter but unfortunately it was added
only to Android.mk. Enabling this parameter didn't have any effect when
Makefile was used to build wpa_supplicant. This commit fixes that problem
and cleans "unused variable" compiler warning.

Signed-off-by: Lauri Hintsala <lauri.hintsala@silabs.com>

wpa_supplicant/Makefile

@@ -317,6 +317,10 @@ CFLAGS += -DCONFIG_INTERWORKING
 NEED_GAS=y
 endif
 
+ifdef CONFIG_NO_ROAMING
+CFLAGS += -DCONFIG_NO_ROAMING
+endif
+
 include ../src/drivers/drivers.mak
 ifdef CONFIG_AP
 OBJS_d += $(DRV_BOTH_OBJS)

wpa_supplicant/events.c

@@ -1286,7 +1286,9 @@ static int wpa_supplicant_need_to_roam(struct wpa_supplicant *wpa_s,
 				       struct wpa_ssid *ssid)
 {
 	struct wpa_bss *current_bss = NULL;
+#ifndef CONFIG_NO_ROAMING
 	int min_diff;
+#endif /* CONFIG_NO_ROAMING */
 
 	if (wpa_s->reassociate)
 		return 1; /* explicit request to reassociate */