log: Add a console driver

It is useful to display log messages on the console. Add a simple driver
to handle this.

Note that this driver outputs to the console, which may be serial or
video. It does not specifically select serial output.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

common/Makefile

@@ -129,5 +129,6 @@ obj-$(CONFIG_FSL_DDR_INTERACTIVE) += cli_simple.o cli_readline.o
 obj-$(CONFIG_CMD_DFU) += dfu.o
 obj-y += command.o
 obj-$(CONFIG_$(SPL_)LOG) += log.o
+obj-$(CONFIG_$(SPL_)LOG_CONSOLE) += log_console.o
 obj-y += s_record.o
 obj-y += xyzModem.o