hikey: remove delay after eMMC initialized

commit 386b14bf64124ebf0368eab33ef07603e0c3138a
Author: Haojian Zhuang <haojian.zhuang@linaro.org>
Date:   Wed Nov 21 09:19:49 2018 +0800

    mmc: poll eMMC status after EXT_CSD command

    EXT_CSD command needs to access data from eMMC device. Add the
    operation of polling eMMC device status. Make sure the command is
    finished.

Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>

A hacked delay time can't fit each eMMC device. Since the above commit
enables the polling operation, remove the hacked delay time now.

Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>