greybus: sdio: add need poll to host caps

As we do not have, yet, a event callback to notify core about changes
we add the MMC_CAP_NEEDS_POLL capability to the rest of the caps
received from the module.

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