cmd: date: Change to use CONFIG_DM_RTC instead of CONFIG_DM_I2C

Currently CONFIG_DM_I2C is used in cmd_date.c for driver model,
but it should be actually CONFIG_DM_RTC.

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