plat: zynqmp: Don't panic() if we can't find the FSBL struct

If we can't find the FSBL handoff struct don't panic and just use the
defaults instead.

We still print a warning to the user to let them know what we couldn't
find it.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
diff --git a/plat/xilinx/zynqmp/plat_startup.c b/plat/xilinx/zynqmp/plat_startup.c
index 32c2db7..d3e182c 100644
--- a/plat/xilinx/zynqmp/plat_startup.c
+++ b/plat/xilinx/zynqmp/plat_startup.c
@@ -161,7 +161,7 @@
 	assert((atf_handoff_addr < BL31_BASE) ||
 	       (atf_handoff_addr > (uint64_t)&__BL31_END__));
 	if (!atf_handoff_addr) {
-		ERROR("BL31: No ATF handoff structure passed\n");
+		WARN("BL31: No ATF handoff structure passed\n");
 		return FSBL_HANDOFF_NO_STRUCT;
 	}