Aspeed have released an updated datasheet (v7) containing the silicon id
for the AST2600 A2. It looks like this:

              SCU004      SCU014
  AST2600-A0  0x05000303  0x05000303
  AST2600-A1  0x05010303  0x05010303
  AST2600-A2  0x05010303  0x05020303
  AST2620-A1  0x05010203  0x05010203
  AST2620-A2  0x05010203  0x05020203

The SCU004 (silicon id 1) value matches SCU014 for A0, but for
subsequent revisions it is hard coded to the A1 value.

Qemu effectively dropped support for the A0 in 7582591a ("aspeed:
Support AST2600A1 silicon revision") as the A0 reset table was removed,
so it makes sense to only support the behaviour of A1 and onwards.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20200916082012.776628-1-joel@jms.id.au>
Signed-off-by: Cédric Le Goater <clg@kaod.org>