sdhci_sysbus: Create SD card device in users, not the device itself

sdhci_sysbus: Create SD card device in users, not the device itself

Move the creation of the SD card device from the sdhci_sysbus
device itself into the boards that create these devices.
This allows us to remove the cannot_instantiate_with_device_add
notation because we no longer call drive_get_next in the device
model.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@xilinx.com>
Message-id: 1455646193-13238-7-git-send-email-peter.maydell@linaro.org