hw/i2c/aspeed: Introduce 'bus-label' to customize bus naming

hw/i2c/aspeed: Introduce 'bus-label' to customize bus naming

On some Aspeed-based machines, multiple I2C controllers may exist
across different components, such as the primary SoC and an external
IO expander or co-processor (e.g., AST1700). Using the current static
naming convention results in object name conflicts when multiple
controllers attempt to instantiate buses with the same ID.

This patch introduces a 'bus-label' property for the Aspeed I2C
controller. This allows higher-level layers, such as the SoC realize
function, to provide a unique identifier for the buses. The I2C bus
object name is then constructed using this label (e.g., "ioexp0.0"
instead of the default "aspeed.i2c.bus.0").

This enhancement ensures unique bus identifiers across the system and
resolves naming conflicts in multi-controller configurations.

Signed-off-by: Kane-Chen-AS <kane_chen@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Tested-by: Nabih Estefan <nabihestefan@google.com>
Reviewed-by: Nabih Estefan <nabihestefan@google.com>
Link: https://lore.kernel.org/qemu-devel/20260112083054.4151945-2-kane_chen@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>