mmc: sdhci-esdhc-imx: SDHCI_CARD_PRESENT does not get cleared

The function esdhc_readl_le intends to clear bit SDHCI_CARD_PRESENT,
when the card detect gpio tells there is no card.  But it does not
clear the bit actually.  The patch gives a fix on that.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: <stable@kernel.org>
Signed-off-by: Chris Ball <cjb@laptop.org>