hw/arm/aspeed: Remove AspeedSoCState dependency from aspeed_soc_uart_set_chr() API

hw/arm/aspeed: Remove AspeedSoCState dependency from aspeed_soc_uart_set_chr() API

Refactor the aspeed_soc_uart_set_chr() helper to remove its dependency
on AspeedSoCState and make the UART character device binding more
generic.

The function now takes SerialMM *uart, uarts_base, and uarts_num
as arguments instead of relying on AspeedSoCState. All affected call
sites in aspeed.c, aspeed_ast27x0-fc.c, and fby35.c are updated
to use the new parameter format.

This improves API flexibility and enables reuse across different Aspeed
SoC variants without requiring access to internal SoC state.

No functional change.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20251013054334.955331-4-jamin_lin@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>