Add user and group for sound_card_init

1. Adds a user and group for sound_card_init, which is currently
used to initialize the calibration value of smart amplifier during
boot time.
2. Add sound_card_init to audio group and cras group.

BUG=b:149437381
TEST=emerge-${BOARD} sound_card_init and verify that sound_card_init account
appear in /build/$BOARD/etc/{passwd,group}

Cq-Depend: chromium:2145748
Change-Id: I25990172dc2e87a79f66ab3142e7d0770a13dd2c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/eclass-overlay/+/2064016
Tested-by: Judy Hsiao <judyhsiao@chromium.org>
Auto-Submit: Judy Hsiao <judyhsiao@chromium.org>
Commit-Queue: Judy Hsiao <judyhsiao@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/profiles/base/accounts/group/audio b/profiles/base/accounts/group/audio
index 739276b..8d7475b 100644
--- a/profiles/base/accounts/group/audio
+++ b/profiles/base/accounts/group/audio
@@ -1,3 +1,3 @@
 group:audio
 gid:18
-users:cras,chronos,volume,midis,rtanalytics
+users:cras,chronos,volume,midis,rtanalytics,sound_card_init
diff --git a/profiles/base/accounts/group/cras b/profiles/base/accounts/group/cras
index 8d31f72..01f27df 100644
--- a/profiles/base/accounts/group/cras
+++ b/profiles/base/accounts/group/cras
@@ -5,4 +5,4 @@
 # The power manager needs to check if audio is playing.
 # The rtanalytics process (running as the rtanalytics user) needs to talk to
 #   cras for audio capture.
-users:chronos,crosvm,power,rtanalytics
+users:chronos,crosvm,power,rtanalytics,sound_card_init
diff --git a/profiles/base/accounts/group/sound_card_init b/profiles/base/accounts/group/sound_card_init
new file mode 100644
index 0000000..7b6d48f
--- /dev/null
+++ b/profiles/base/accounts/group/sound_card_init
@@ -0,0 +1,4 @@
+# Group for Chromium OS sound card initializer
+group:sound_card_init
+gid:20147
+users:
diff --git a/profiles/base/accounts/user/sound_card_init b/profiles/base/accounts/user/sound_card_init
new file mode 100644
index 0000000..5191af1
--- /dev/null
+++ b/profiles/base/accounts/user/sound_card_init
@@ -0,0 +1,6 @@
+user:sound_card_init
+uid:20147
+gid:20147
+gecos:Chromium OS sound card initializer
+home:/dev/null
+shell:/bin/false