spl: fix stack usage check if gd is not initialized

Most platforms do not set up gd->start_addr_sp in SPL. Since this is
required for CONFIG_SPL_SYS_REPORT_SACK_F_USAGE to work correctly, set
up gd->start_addr_sp in SPL to the value passed to
board_init_f_init_reserve if it is not set yet.

Fixes: d8c0332031 ("spl: implement stack usage check")
Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
diff --git a/common/init/board_init.c b/common/init/board_init.c
index e521069..3bc7994 100644
--- a/common/init/board_init.c
+++ b/common/init/board_init.c
@@ -19,6 +19,19 @@
 #endif /* !CONFIG_X86 && !CONFIG_ARM */
 
 /**
+ * This function is called from board_init_f_init_reserve to set up
+ * gd->start_addr_sp for stack protection if not already set otherwise
+ */
+__weak void board_init_f_init_stack_protection_addr(ulong base)
+{
+#if CONFIG_IS_ENABLED(SYS_REPORT_STACK_F_USAGE)
+	/* set up stack pointer for stack usage if not set yet */
+	if (!gd->start_addr_sp)
+		gd->start_addr_sp = base;
+#endif
+}
+
+/**
  * This function is called after the position of the initial stack is
  * determined in gd->start_addr_sp. Boards can override it to set up
  * stack-checking markers.
@@ -129,6 +142,10 @@
 #if !defined(CONFIG_ARM)
 	arch_setup_gd(gd_ptr);
 #endif
+
+	if (CONFIG_IS_ENABLED(SYS_REPORT_STACK_F_USAGE))
+		board_init_f_init_stack_protection_addr(base);
+
 	/* next alloc will be higher by one GD plus 16-byte alignment */
 	base += roundup(sizeof(struct global_data), 16);