mmc: sdhci: Enable 8-bit bus width only for 3.0 spec onwards

CAP register don't have any information for 8-bit buswidth support
on 2.0 sdhci spec, only from 3.0 onwards bit[18] got this information.

Due to this misassignment in sdhci, mmc is setting 8-bit buswidth using
mmc_set_bus_width even if controller doesn't support.
Below change has code information.
"mmc: Properly determine maximum supported bus width"
(sha1: 7798f6dbd5)

Bug log: <mmc plus and emmc cards)
-------
zynq-uboot> mmcinfo
Error detected in status(0x208100)!
Device: zynq_sdhci
Manufacturer ID: fe
.....

So enable 8-bit support only for 3.0 spec using CAP and for below 3.0
assign mmc->host_caps = MMC_MODE_8BIT on respective platform driver
if host have a support.

Signed-off-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>

drivers/mmc/sdhci.c

@@ -486,8 +486,10 @@ int add_sdhci(struct sdhci_host *host, u32 max_clk, u32 min_clk)
 		mmc->voltages |= host->voltages;
 
 	mmc->host_caps = MMC_MODE_HS | MMC_MODE_HS_52MHz | MMC_MODE_4BIT;
-	if (caps & SDHCI_CAN_DO_8BIT)
-		mmc->host_caps |= MMC_MODE_8BIT;
+	if ((host->version & SDHCI_SPEC_VER_MASK) >= SDHCI_SPEC_300) {
+		if (caps & SDHCI_CAN_DO_8BIT)
+			mmc->host_caps |= MMC_MODE_8BIT;
+	}
 	if (host->host_caps)
 		mmc->host_caps |= host->host_caps;