mmc: core: fix typo in mmc_stop_host

mmc_stop_host() should be calling mmc_unregister_extcon() to deregister
from the extcon framework but instead it was calling mmc_register_extcon().
Fixed this typo.

Change-Id: I6a235b9b34f01b29aeebf344cb2837f927b47d9c
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 0bf89b4..978dd9a 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -4472,7 +4472,7 @@
 
 	BUG_ON(host->card);
 
-	mmc_register_extcon(host);
+	mmc_unregister_extcon(host);
 
 	mmc_claim_host(host);
 	mmc_power_off(host);