[Fix] BF16 (and FP16) bias is not in BF16 (or FP16)

Add the output (bias) type to the shape list of convolution operators
so that the output (bias) type can be retrieved during test gen.
Remove the accumulator type info from the table since it is inferable.

Signed-off-by: TatWai Chong <tatwai.chong@arm.com>
Change-Id: I1f30897e2a53d444b1370301b7aca5ea12af1e3b