libstb/secvar: Ensure secvar_set_status() is called once

Remove the check to see if the "status" property already exists. This
function is intended to only be called once so failing an assert is
fine since it indicates a programming error.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>

libstb/secvar/secvar_devtree.c

@@ -47,11 +47,8 @@ void secvar_set_status(const char *status)
 	if (!secvar_node)
 		return; // Fail boot?
 
-	if (dt_find_property(secvar_node, "status"))
-		return;
-
+	/* This function should only be called once */
 	dt_add_property_string(secvar_node, "status", status);
-	// Fail boot if not successful?
 }