drivers: mmc: fix issue raised by source code analyzer tool

Fix the below reported issues by source code analyzer.

1) Pointer 'ext_csd' returned from call to function 'mmc_get_ext_csd'
may be NULL and will be dereferenced at ext_csd[EXT_CSD_CMDQ] in
mmc_test_awake_ext_csd(), causing NUll pointer derefernce.

2) Array 'sdhci_slot' of size 2 may use index value(s) -1 as below,
when ret = 0.

	sdhci_slot[ret-1] = msm_host;

3) Variable 'host->lock' locked ,And was not unlocked when below
condition occurs in sdhci_irq().

	if (!mmc_card_and_host_support_async_int(host->mmc))
		return IRQ_NONE;

CRs-Fixed: 1000387
Change-Id: Iec6ecef1bf940e720c871be58b265394904f0cf1
Signed-off-by: Pavan Anamula <pavana@codeaurora.org>

drivers/mmc/core/mmc.c

@@ -2439,7 +2439,7 @@ static int mmc_test_awake_ext_csd(struct mmc_host *host)
 	struct mmc_card *card = host->card;
 
 	err = mmc_get_ext_csd(card, &ext_csd);
-	if (err) {
+	if (err || !ext_csd) {
 		pr_err("%s: %s: mmc_get_ext_csd failed (%d)\n",
 			mmc_hostname(host), __func__, err);
 		return err;

drivers/mmc/host/sdhci-msm.c

@@ -3936,7 +3936,7 @@ static int sdhci_msm_probe(struct platform_device *pdev)
 	/* Extract platform data */
 	if (pdev->dev.of_node) {
 		ret = of_alias_get_id(pdev->dev.of_node, "sdhc");
-		if (ret < 0) {
+		if (ret <= 0) {
 			dev_err(&pdev->dev, "Failed to get slot index %d\n",
 				ret);
 			goto pltfm_free;

drivers/mmc/host/sdhci.c

@@ -3089,8 +3089,10 @@ static irqreturn_t sdhci_irq(int irq, void *dev_id)
 
 	if (!host->clock && host->mmc->card &&
 			mmc_card_sdio(host->mmc->card)) {
-		if (!mmc_card_and_host_support_async_int(host->mmc))
+		if (!mmc_card_and_host_support_async_int(host->mmc)) {
+			spin_unlock(&host->lock);
 			return IRQ_NONE;
+		}
 		/*
 		 * async card interrupt is level sensitive and received
 		 * when clocks are off.