procd: emit events for sound subsystem

procd: emit events for sound subsystem

Useful e.g. for plugable USB-soundcards.
With this change an event/hotplug-call looks like:

ACTION: add DEVNAME: snd/timer DEVPATH: /devices/virtual/sound/timer SUBSYSTEM: sound
ACTION: add DEVNAME:  DEVPATH: /devices/platform/ehci-platform/usb1/1-1/1-1:1.0/sound/card0 SUBSYSTEM: sound
ACTION: add DEVNAME: snd/controlC0 DEVPATH: /devices/platform/ehci-platform/usb1/1-1/1-1:1.0/sound/card0/controlC0 SUBSYSTEM: sound
ACTION: add DEVNAME: snd/pcmC0D0p DEVPATH: /devices/platform/ehci-platform/usb1/1-1/1-1:1.0/sound/card0/pcmC0D0p SUBSYSTEM: sound
ACTION: add DEVNAME: snd/pcmC0D0c DEVPATH: /devices/platform/ehci-platform/usb1/1-1/1-1:1.0/sound/card0/pcmC0D0c SUBSYSTEM: sound
ACTION: add DEVNAME: dsp DEVPATH: /devices/platform/ehci-platform/usb1/1-1/1-1:1.0/sound/card0/dsp SUBSYSTEM: sound
ACTION: add DEVNAME: audio DEVPATH: /devices/platform/ehci-platform/usb1/1-1/1-1:1.0/sound/card0/audio SUBSYSTEM: sound
ACTION: add DEVNAME: mixer DEVPATH: /devices/platform/ehci-platform/usb1/1-1/1-1:1.0/sound/card0/mixer SUBSYSTEM: sound

This fixes #21466.

Signed-off-by: Bastian Bittorf <bittorf@bluebottle.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@48366 3c298f89-4303-0410-b956-a3cf2f4a3e73