cmd: add Kconfig option for 'date' command

Signed-off-by: Chris Packham <judge.packham@gmail.com>
[trini: default y if DM_RTC, re-sync]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/mx31ads_defconfig b/configs/mx31ads_defconfig
index 6747ee0..c9ba697 100644
--- a/configs/mx31ads_defconfig
+++ b/configs/mx31ads_defconfig
@@ -5,5 +5,6 @@
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_DHCP=y
 CONFIG_CMD_PING=y
+CONFIG_CMD_DATE=y
 # CONFIG_MMC is not set
 CONFIG_MTD_NOR_FLASH=y