greybus: sdio: check number of blocks in transfer

Before initiating a transfers, check if the command (for single block)
match the number of blocks in the request.

While at it, fix also a missing break.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>