arm: Fix some inconsistent debug-UART CONFIG options

A few boards enable CONFIG_DEBUG_UART_BOARD_INIT but do not define the
required init function. Fix this by disabling the debug UART.

With snow the debug UART is enabled but the driver CONFIG is not. Fix this
too.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/evb-rk3128_defconfig b/configs/evb-rk3128_defconfig
index e446a22..544d6de 100644
--- a/configs/evb-rk3128_defconfig
+++ b/configs/evb-rk3128_defconfig
@@ -6,6 +6,7 @@
 CONFIG_ENV_OFFSET=0x0
 CONFIG_DEFAULT_DEVICE_TREE="rk3128-evb"
 CONFIG_ROCKCHIP_RK3128=y
+# CONFIG_DEBUG_UART_BOARD_INIT is not set
 CONFIG_DEBUG_UART_BASE=0x20068000
 CONFIG_DEBUG_UART_CLOCK=24000000
 CONFIG_DEBUG_UART=y