information is set to FreeBSD. It had been falling through to the end
of linux_ioctl_sound() and returning ENOIOCTL. Noticed when running the
Linux ALSA amixer tool.
Add a LINUX_SOUND_MIXER_READ_CAPS ioctl which is used by the Skype
v2.1.0.81 binary.
Reviewed by: gavin
MFC after: 2 weeks