app: aboot: check for buffer over reads
app: aboot: check for buffer over reads

Added checks for buffer over reads while reading
the sparse image from RAM and also added check on
chunk header size.

Change-Id: I1e320bbbbf945e813216d169ced851836b862de8

CanarySolutions/little-kernel,CanarySolutions/little-kernel,CanarySolutions/little-kernel,CanarySolutions/little-kernel,CanarySolutions/little-kernel