hw/net/ftgmac100: Convert to DEFINE_TYPES() with inlined TypeInfo

Replace the legacy type_register_static()/type_init() registration
pattern with the modern DEFINE_TYPES() macro.

Inline 2 standalone TypeInfo variables (ftgmac100_info,
aspeed_mii_info) directly into the 'ftgmac100_types[]' array,
removing the need for separate declarations. Note that this file
covers both the Faraday FTGMAC100 Gigabit Ethernet controller and
the Aspeed MII controller, which share the same type registration.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20260601024959.2347639-24-jamin_lin@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>