arm64: versal: Fix emmc boot mode boot_target issue

Emmc boot devcie is mounted to sdhci@f1050000 controller on versal, while
in emmc boot mode, boot tragets are set to mmc0. So removed mmc0 and using
the dev seq number from the sdhci@f1050000 controller.
Dev seq number is setup based on DT aliases that's why needs to be setup at
run time.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/board/xilinx/versal/board.c b/board/xilinx/versal/board.c
index 23bb6b9..4572447 100644
--- a/board/xilinx/versal/board.c
+++ b/board/xilinx/versal/board.c
@@ -130,7 +130,14 @@
 		break;
 	case EMMC_MODE:
 		puts("EMMC_MODE\n");
-		mode = "mmc0";
+		if (uclass_get_device_by_name(UCLASS_MMC,
+					      "sdhci@f1050000", &dev)) {
+			puts("Boot from EMMC but without SD1 enabled!\n");
+			return -1;
+		}
+		debug("mmc1 device found at %p, seq %d\n", dev, dev->seq);
+		mode = "mmc";
+		bootseq = dev->seq;
 		break;
 	case SD_MODE:
 		puts("SD_MODE\n");