Revert "Remove proc access from hal_audio."

Reason: breaks "Ok google". Soundtrigger module needs to access /proc/asound/pcm.

This reverts commit 5cccb249.

Bug: 67930353
Change-Id: I67e0912a6795b3715a3321d3fe5147f49cebc9b5

public/hal_audio.te

@@ -13,6 +13,7 @@ userdebug_or_eng(`
   allow hal_audio audiohal_data_file:file create_file_perms;
 ')
 
+r_dir_file(hal_audio, proc)
 r_dir_file(hal_audio, proc_asound)
 allow hal_audio audio_device:dir r_dir_perms;
 allow hal_audio audio_device:chr_file rw_file_perms;