fs: yaffs2: update sources to 3.x compatability

 tag: pre-driver-refactoring
 git://www.aleph1.co.uk/yaffs2
 notes: minor changes made to compile in the kernel

Change-Id: I85606e69d03c38135cf1a1fdc5747171ab24aa4f
supersonic: initial import

Change-Id: Iccd5cfb3b2b9c9b74c05a85e0ace1e51f73bdc0e