sdhci: don't raise a command index error for an unexpected response

This deletes a block of code that raised a command index error if a
command returned response data, but the guest did not set the
appropriate bits in the response register to handle such a response. I
cannot find any documentation that suggests the controller should
behave in this way, the error code doesn't make sense (command index
error is defined for the case where the index in a response does not
match that of the issued command), and in at least one case (CMD23
issued by UEFI on Raspberry Pi 2), actual hardware does not do this.

Signed-off-by: Andrew Baumann <Andrew.Baumann@microsoft.com>
Reviewed-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Message-id: 1450738069-18664-3-git-send-email-Andrew.Baumann@microsoft.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>