payload: rename dummy payload to test payload

Use a more neutral term more representative of this payload intent.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

firmware/payloads/test_main.c

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2018 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *   Anup Patel <anup.patel@wdc.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <sbi/sbi_ecall_interface.h>
+
+#define wfi()						\
+do {							\
+	__asm__ __volatile__ ("wfi" ::: "memory");	\
+} while (0)
+
+static void sbi_puts(const char *str)
+{
+	while (*str) {
+		SBI_ECALL_1(SBI_ECALL_CONSOLE_PUTCHAR, *str);
+		str++;
+	}
+}
+
+void test_main(unsigned long a0, unsigned long a1)
+{
+	sbi_puts("\nTest payload running\n");
+
+	while (1)
+		wfi();
+}