xilinx: zynqmp: Set modeboot env variable in eMMC bootmode

Set environment variable modeboot to "emmcboot" in case of eMMC boot
mode.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/c61231e4b8c6118862dfc82e923211637bf29991.1631688736.git.michal.simek@xilinx.com
diff --git a/board/xilinx/zynqmp/zynqmp.c b/board/xilinx/zynqmp/zynqmp.c
index ea15e62..000a7cd 100644
--- a/board/xilinx/zynqmp/zynqmp.c
+++ b/board/xilinx/zynqmp/zynqmp.c
@@ -672,6 +672,7 @@
 
 		mode = "mmc";
 		bootseq = dev_seq(dev);
+		env_set("modeboot", "emmcboot");
 		break;
 	case SD_MODE:
 		puts("SD_MODE\n");