hostapd(hidl): Add HIDL interface skeletal code

Adding support for HIDL IPC in hostapd. This CL only adds the skeletal
framework for supporting HIDL interface implementation.

There is also a change in the hostapd.h to fix a C++ compilation error.

Bug: 36646171
Test: Compiles with CONFIG_CTRL_IFACE_HIDL=y in android.config
Change-Id: I4a7047a56f8e9be1ed51f2315df707ef5daddc11
diff --git a/hostapd/android.config b/hostapd/android.config
index 08d21f0..3e40aa1 100644
--- a/hostapd/android.config
+++ b/hostapd/android.config
@@ -210,3 +210,7 @@
 # /dev/urandom earlier in boot' seeds /dev/urandom with that entropy before
 # either wpa_supplicant or hostapd are run.
 CONFIG_NO_RANDOM_POOL=y
+
+# Add support for Hidl control interface
+# Only applicable for Android platforms.
+CONFIG_CTRL_IFACE_HIDL=n