aspeed: introduce a new UART0 device name

aspeed: introduce a new UART0 device name

The Aspeed datasheet refers to the UART controllers
as UART1 - UART13 for the ast10x0, ast2600, ast2500
and ast2400 SoCs and the Aspeed ast2700 introduces an UART0
and the UART controllers as UART0 - UART12.

To keep the naming in the QEMU models
in sync with the datasheet, let's introduce a new  UART0 device name
and do the required adjustements.

Signed-off-by: Troy Lee <troy_lee@aspeedtech.com>
Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
[ clg: - Kept original assert() in aspeed_soc_uart_set_chr()
       - Fixed 'i' range in connect_serial_hds_to_uarts() loop ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>