[sdmmc] Change internal read/write retries

This can fix busy errors when writing to sd cards.
Additionally it now returns properly on success

ipl/main.c

@@ -850,8 +850,8 @@ int dump_emmc_part(char *sd_path, sdmmc_storage_t *storage, emmc_part_t *part)
 			EPRINTFARGS("Error reading %d blocks @ LBA %08X from eMMC (try %d), retrying...",
 				num, lba_curr, ++retryCount);
 
-			sleep(500000);
-			if (retryCount >= 10)
+			sleep(150000);
+			if (retryCount >= 3)
 			{
 				EPRINTFARGS("\nFailed to read %d blocks @ LBA %08X from eMMC. Aborting..\n",
 				num, lba_curr);

ipl/sdmmc.c

@@ -165,15 +165,27 @@ static int _sdmmc_storage_readwrite(sdmmc_storage_t *storage, u32 sector, u32 nu
 	while (num_sectors)
 	{
 		u32 blkcnt = 0;
-		//Retry once on error.
-		if (!_sdmmc_storage_readwrite_ex(storage, &blkcnt, sector, MIN(num_sectors, 0xFFFF), bbuf, is_write))
-			if (!_sdmmc_storage_readwrite_ex(storage, &blkcnt, sector, MIN(num_sectors, 0xFFFF), bbuf, is_write))
-				return 0;
+		//Retry 9 times on error.
+		u32 retries = 10;
+		do
+		{
+			if (_sdmmc_storage_readwrite_ex(storage, &blkcnt, sector, MIN(num_sectors, 0xFFFF), bbuf, is_write))
+				goto out;
+			else
+				retries--;
+
+			sleep(500000);
+
+		} while (retries);
+		return 0;
+
+out:;
 		DPRINTF("readwrite: %08X\n", blkcnt);
 		sector += blkcnt;
 		num_sectors -= blkcnt;
 		bbuf += 512 * blkcnt;
 	}
+	return 1;
 }
 
 int sdmmc_storage_read(sdmmc_storage_t *storage, u32 sector, u32 num_sectors, void *buf)