[ARM PATCH] 1332/1: DMA Scatter-Gather Primitives for SA-1111 Bounce Buffer Layer

Patch from Christopher Hoover

- implements the dma scatter-gather primitives for the SA-1111 bounce
buffer layer.  these are required by usb-storage.

- adds (optionally) a tiny bit of statistics

- adjust the large buffer pool down to 4KiB (suggested by the stats)