greybus: sdio: avoid extra memory operation at data transfer

Right now greybus sdio uses the greybus operation_sync to transfer data,
this will imply an extra memcpy at greybus core that we can avoid.

Also with this change we remove the need for an extra buffer to store
intermediate copy.

So, let us create the operation and do the memory operations in the sdio
driver.

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