rockchip: spl: Drop out of scope debug message related to uart init

Debug uart is no more inited in board_init_f function: remove this
debug message from board_init_f. If an earliest-as-possible message
after debug uart initialization is needed, enable DEBUG_UART_ANNOUNCE
Kconfig option, instead.

Signed-off-by: Massimo Pegorer <massimo.pegorer+oss@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>