aspeed: Deprecate the qcom-dc-scm-v1-bmc and qcom-firework-bmc machines

aspeed: Deprecate the qcom-dc-scm-v1-bmc and qcom-firework-bmc machines

There are no functional tests for the 'qcom-dc-scm-v1-bmc' and
'qcom-firework-bmc' machines which makes harder to determine when
something becomes deprecated or unused.

Since the machines do not rely on any specific device models, they can
be replaced by the 'ast2600-evb' machine using the 'fmc-model' option
to specify the flash type. The I2C devices connected to the board can
be defined via the QEMU command line.

Cc: Jae Hyun Yoo <quic_jaehyoo@quicinc.com>
Link: https://lore.kernel.org/qemu-devel/20251007141604.761686-3-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>