mmc: sdio: Allow sdio operations in other threads during sdio_add_func()

This fixes a bug introduced by 807e8e40 ("mmc: Fix sd/sdio/mmc
initialization frequency retries") that prevented SDIO drivers from
performing SDIO commands in their probe routines -- the above patch
called mmc_claim_host() before sdio_add_func(), which causes a deadlock
if an external SDIO driver calls sdio_claim_host().

Fix tested on an OLPC XO-1.75 with libertas on SDIO.
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>
Reviewed-and-Tested-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/core/sdio.c

@@ -792,7 +792,6 @@ int mmc_attach_sdio(struct mmc_host *host)
 	 */
 	mmc_release_host(host);
 	err = mmc_add_card(host->card);
-	mmc_claim_host(host);
 	if (err)
 		goto remove_added;
 
@@ -805,12 +804,12 @@ int mmc_attach_sdio(struct mmc_host *host)
 			goto remove_added;
 	}
 
+	mmc_claim_host(host);
 	return 0;
 
 
 remove_added:
 	/* Remove without lock if the device has been added. */
-	mmc_release_host(host);
 	mmc_sdio_remove(host);
 	mmc_claim_host(host);
 remove: