mmc: fsl_esdhc_imx: Handle the "broken-cd" property

mmc: fsl_esdhc_imx: Handle the "broken-cd" property

When no GPIO is used to read the card detect status the following
error is seen:

MMC:   FSL_SDHC: 0, FSL_SDHC: 1
Loading Environment from MMC... MMC: no card present
*** Warning - No block device, using default environment

Fix it by handling the "broken-cd" property in the same way
that drivers/mmc/sdhci.c does, which considers that the SD card
is present when the "broken-cd" property is passed.

Tested on a imx6ul-evk board.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Stefano Babic <sbabic@denx.de>