mmc: drop mention of IN_PROGRESS status

The IN_PROGRESS macro has been removed in commit bd47c13583f (mmc: Fix
splitting device initialization). Remove it from the mmc_start_init()
function description.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
diff --git a/include/mmc.h b/include/mmc.h
index 534c317..1729292 100644
--- a/include/mmc.h
+++ b/include/mmc.h
@@ -759,7 +759,7 @@
  * initializatin.
  *
  * @param mmc	Pointer to a MMC device struct
- * @return 0 on success, IN_PROGRESS on waiting for OCR status, <0 on error.
+ * @return 0 on success, <0 on error.
  */
 int mmc_start_init(struct mmc *mmc);