hw/arm/aspeed: Split GB200NVL machine into a separate source file for maintainability

hw/arm/aspeed: Split GB200NVL machine into a separate source file for maintainability

This commit moves the Nvidia GB200NVL BMC machine implementation out of
aspeed.c into a new standalone file aspeed_ast2600_gb200nvl.c.

This refactor continues the modularization effort for Aspeed platform support,
placing each board’s initialization logic in its own dedicated source file.
It improves code maintainability, readability, and simplifies adding new
platforms without increasing the complexity of aspeed.c.

Key updates include:
- Moved GB200NVL_BMC_HW_STRAP1 and GB200NVL_BMC_HW_STRAP2 macro definitions into the new file.
- Moved gb200nvl_bmc_i2c_init() and its related FRUID setup into the new file.
- Moved aspeed_machine_gb200nvl_class_init() and type registration logic out of aspeed.c.
- Removed gb200nvl_bmc_fruid[] and its length definition from aspeed_eeprom.c/h.
- Added aspeed_ast2600_gb200nvl.c to the Meson build system (meson.build).
- Cleaned up all GB200NVL-specific code and data from aspeed.c and aspeed_eeprom.c.

No functional changes.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20251104031325.146374-25-jamin_lin@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>