rockchip: rk322x: move board_debug_uart_init() to rk322x.c

rockchip: rk322x: move board_debug_uart_init() to rk322x.c

Move the function to soc file so
that we can find all the soc/board setting in soc file and
use a common board file later for all rockchip SoCs.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
[Fixed up header-list to not break FASTBOOT:]
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>