xilinx: zynq: Generate dfu for SPI only when enabled

Bitmain S9 board is not enabling SPI that's why CONFIG_SYS_SPI_U_BOOT_OFFS
symbol is not present which ends in build failure when EFI/DFU
infrastructure is enabled.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/3ea0572dbda8f21270c00a77528eb6ec954c7c40.1699866313.git.michal.simek@amd.com
diff --git a/board/xilinx/zynq/board.c b/board/xilinx/zynq/board.c
index 3b6581e..6c36591 100644
--- a/board/xilinx/zynq/board.c
+++ b/board/xilinx/zynq/board.c
@@ -184,6 +184,7 @@
 			 "mmc 0=boot.bin fat 0 1;"
 			 "%s fat 0 1", CONFIG_SPL_FS_LOAD_PAYLOAD_NAME);
 		break;
+#if defined(CONFIG_SPL_SPI_LOAD)
 	case ZYNQ_BM_QSPI:
 		snprintf(buf, DFU_ALT_BUF_LEN,
 			 "sf 0:0=boot.bin raw 0 0x1500000;"
@@ -191,6 +192,7 @@
 			 CONFIG_SPL_FS_LOAD_PAYLOAD_NAME,
 			 CONFIG_SYS_SPI_U_BOOT_OFFS);
 		break;
+#endif
 	default:
 		return;
 	}