This fixes a bug in the audio driver which came from an
incorrect conversion from static to dynamic URB allocation.
It's against 2.5.5
  
I noticed this while trying to see exactly how ISO transfers
get used.  The bug is that while originally the driver statically
allocated several structures {urb + N * iso packet descriptors},
the update forgot to allocate the ISO descriptors.
    
Likely not many folk noticed this on 32 bit machines, where
sizeof urb == 92, because kmalloc rounds that up to 128,
adding 36 bytes of external padding.  The ISO descriptors
took up 32 bytes of that, which "just happened" to already
have been allocated but unused.