[Yaffs] YAFFS block smmary test

Hi All

On the weekend I set up an Overo board (equivalent to a slower Beagleboard)
with yaffs to get a datapoint for the block summary speed up. Flash speed was
quite slow due to a slow mtd implementation.

I filled almost 250Mbytes with 1MB files and observed the following mount
times:

Mount with full scan using no checkpoint or block summary info: 8.67 seconds
Mount with block summary: 1.02 seconds
Mount with checkpoint: 0.17 seconds

-- CHarles