cmd: Rename CMD_MISC to CMD_SLEEP

The "cmd/Kconfig" has a TODO description for CMD_MISC that it should
really be named as CMD_SLEEP. Change it in the whole source tree.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
diff --git a/configs/comtrend_ar5387un_ram_defconfig b/configs/comtrend_ar5387un_ram_defconfig
index 8d1de33..80bafb0 100644
--- a/configs/comtrend_ar5387un_ram_defconfig
+++ b/configs/comtrend_ar5387un_ram_defconfig
@@ -32,7 +32,7 @@
 CONFIG_CMD_USB=y
 CONFIG_CMD_MII=y
 CONFIG_CMD_PING=y
-# CONFIG_CMD_MISC is not set
+# CONFIG_CMD_SLEEP is not set
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_NET_RANDOM_ETHADDR=y
 # CONFIG_DM_DEVICE_REMOVE is not set