Undefine NAN before defining it again

After upgrading libc++, math.h happens to be included at the point
where this file tries to define NAN. Redefining a macro to a different
value is an error, but #undef'ing a macro is OK even if the macro isn't
actually defined.

Bug: b/175635923
Test: treehugger
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:dd390faa2fcb49ce0e0ebc6ef180118ec370f957)
Merged-In: Ie8e3e87189bcd7ed8fccccfc0a79e04a5bfda16b
Change-Id: Ie8e3e87189bcd7ed8fccccfc0a79e04a5bfda16b
diff --git a/wifi/aidl/default/wifi_feature_flags.cpp b/wifi/aidl/default/wifi_feature_flags.cpp
index 3c9f042..35b4b4a 100644
--- a/wifi/aidl/default/wifi_feature_flags.cpp
+++ b/wifi/aidl/default/wifi_feature_flags.cpp
@@ -122,6 +122,7 @@
 #define AP IfaceConcurrencyType::AP
 #define AP_BRIDGED IfaceConcurrencyType::AP_BRIDGED
 #define P2P IfaceConcurrencyType::P2P
+#undef NAN  // undefine NAN from math.h
 #define NAN IfaceConcurrencyType::NAN_IFACE
 static const std::vector<IWifiChip::ChipMode> kChipModesPrimary{
         {kMainModeId, legacyToChipConcurrencyComboList({WIFI_HAL_INTERFACE_COMBINATIONS})},