meson: Add deviceprovider changes to directsoundsrc

These were missed when they were added to Makefile.am
diff --git a/sys/directsound/meson.build b/sys/directsound/meson.build
index efe9a1e..81e780c 100644
--- a/sys/directsound/meson.build
+++ b/sys/directsound/meson.build
@@ -1,14 +1,23 @@
 directsoundsrc_sources = [
   'gstdirectsoundsrc.c',
+  'gstdirectsounddevice.c',
   'gstdirectsoundplugin.c',
 ]
 
+directsoundsrc_device_flags = [
+  '-DGstDirectSoundDeviceProvider=GstDirectSoundSrcDeviceProvider',
+  '-DGstDirectSoundDeviceProviderClass=GstDirectSoundSrcDeviceProviderClass',
+  '-DGstDirectSoundDevice=GstDirectSoundSrcDevice',
+  '-DGstDirectSoundDeviceClass=GstDirectSoundSrcDeviceClass',
+  '-DGST_DIRECTSOUND_SRC_DEVICE_PROVIDER=1'
+]
+
 if host_system == 'windows' and cc.has_header('dsound.h')
   directsoundsrc_dep = [cc.find_library('dsound'), cc.find_library('winmm'), cc.find_library('ole32')]
 
   gstdirectsoundsrc = library('gstdirectsoundsrc',
     directsoundsrc_sources,
-    c_args : gst_plugins_bad_args,
+    c_args : gst_plugins_bad_args + directsoundsrc_device_flags,
     include_directories : [configinc],
     dependencies : [gstaudio_dep] + directsoundsrc_dep,
     install : true,