log: Add a 'log level' command

Add a command for adjusting the log level.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/cmd/Makefile b/cmd/Makefile
index f9eb760..00e3869 100644
--- a/cmd/Makefile
+++ b/cmd/Makefile
@@ -76,6 +76,7 @@
 obj-$(CONFIG_CMD_LED) += led.o
 obj-$(CONFIG_CMD_LICENSE) += license.o
 obj-y += load.o
+obj-$(CONFIG_CMD_LOG) += log.o
 obj-$(CONFIG_ID_EEPROM) += mac.o
 obj-$(CONFIG_CMD_MD5SUM) += md5sum.o
 obj-$(CONFIG_CMD_MEMORY) += mem.o