sdhci: add quirk property for card insert interrupt status on Raspberry Pi

sdhci: add quirk property for card insert interrupt status on Raspberry Pi

This quirk is a workaround for the following hardware behaviour, on
which UEFI (specifically, the bootloader for Windows on Pi2) depends:

1. at boot with an SD card present, the interrupt status/enable
   registers are initially zero
2. upon enabling it in the interrupt enable register, the card insert
   bit in the interrupt status register is immediately set
3. after a subsequent controller reset, the card insert interrupt does
   not fire, even if enabled in the interrupt enable register

Signed-off-by: Andrew Baumann <Andrew.Baumann@microsoft.com>
Message-id: 1456436130-7048-3-git-send-email-Andrew.Baumann@microsoft.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>