arm64: zynqmp: Generate dfu_alt_info based on multiboot register

Commit 2c8a09219cdb ("arm64: zynqmp: Add multiboot support for SPL/SPI
offset calculation") enabled u-boot.itb offset calculation based on
multiboot register. It is also good to reflect location of u-boot.itb image
for dfu_alt generation.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/5abc5f3047ce586b4d2740b5eea775d063295e28.1702906896.git.michal.simek@amd.com
diff --git a/board/xilinx/zynqmp/zynqmp.c b/board/xilinx/zynqmp/zynqmp.c
index 59feaaf..e3700f0 100644
--- a/board/xilinx/zynqmp/zynqmp.c
+++ b/board/xilinx/zynqmp/zynqmp.c
@@ -670,7 +670,7 @@
 		len += snprintf(buf + len, DFU_ALT_BUF_LEN,
 			       ";%s raw 0x%x 0x500000",
 			       CONFIG_SPL_FS_LOAD_PAYLOAD_NAME,
-			       CONFIG_SYS_SPI_U_BOOT_OFFS);
+			       multiboot * SZ_32K + CONFIG_SYS_SPI_U_BOOT_OFFS);
 #endif
 		break;
 	default: