[i.MX93][i.MX95] make debug UART base address configurable via variable
Let the debug UART base address be configurable via IMX_BOOT_UART_BASE variable, as is supported on i.MX8M. This variable is setup by the Yocto layer via the configuration variable SOC_ATF_BOOT_UART_BASE.
Signed-off-by: Gianfranco Mariotti gianfranco.mariotti@seco.com