Define vintf fragment as a module

Define vintf fragment as a module, so it can be used from multiple
soong-defined modules.

Bug: 322089980
Test: aosp_cf_x86_64_phone build succeeded
(cherry picked from https://android-review.googlesource.com/q/commit:8c1af351129febcebea9ddc5f8e584a6a6a3bd97)
Change-Id: I817efd443e49439e4134fca8bd3fd034bbbcc3cc
diff --git a/hostapd/Android.mk b/hostapd/Android.mk
index 35ada83..40c528b 100644
--- a/hostapd/Android.mk
+++ b/hostapd/Android.mk
@@ -1178,7 +1178,7 @@
 LOCAL_MODULE_TAGS := optional
 LOCAL_PROPRIETARY_MODULE := true
 LOCAL_MODULE_RELATIVE_PATH := hw
-LOCAL_VINTF_FRAGMENTS := android.hardware.wifi.hostapd.xml
+LOCAL_REQUIRED_MODULES += android.hardware.wifi.hostapd.xml
 ifdef CONFIG_DRIVER_CUSTOM
 LOCAL_STATIC_LIBRARIES := libCustomWifi
 endif