MLBEDSW-9868: Adjust BufferReader asserts to always allow index 0
Index 0 is unstrided so we can always allow reading that index
regardless of stride. Also added a few more asserts.
Signed-off-by:
Johan Gunnarsson <johan.gunnarsson@arm.com>
Change-Id: Icf7ac8c46665d4e651232d0c0ba66733dce99dc6