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>

include/mmc.h

@@ -759,7 +759,7 @@ int mmc_set_bkops_enable(struct mmc *mmc);
  * 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);