mmc: sdhci: Add a quirk to add delay during completion of sdhci_send_cmd

MMC host controller requires a delay between every sdhci_send_cmd()
execution. In s5p_mmc driver (s5p_sdhci replaces this driver), a delay
of 1000us was provided after every mmc_send_cmd() call. Adding a quirk
in current sdhci driver to replicate the behaviour.

Without this delay, MMC initialization on Origen board fails with
following error messages.

Timeout for status update!
mmc fail to send stop cmd

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>