mmc: sdhci-pci: Fix card detect race for Intel BXT/APL
Intel BXT/APL use a card detect GPIO however the host controller
will not enable bus power unless it's card detect also reflects
the presence of a card. Unfortunately those 2 things race which
can result in commands not starting, after which the controller
does nothing and there is a 10 second wait for the driver's
10-second timer to timeout.
That is fixed by having the driver look also at the present state
register to determine if the card is present. Consequently, provide
a 'get_cd' mmc host operation for BXT/APL that does that.