audio: remove HAS_AUDIO

Several targets can have wavcapture/-soundhw support via PCI cards.
HAS_AUDIO is a useless limitation, remove it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1366303444-24620-4-git-send-email-pbonzini@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>