riscv: Add tests for riscv module loading

Add test cases for the two main groups of relocations added: SUB and
SET, along with uleb128.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/20231101-module_relocations-v9-3-8dfa3483c400@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/tests/module_test/test_sub64.S

@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 Rivos Inc.
+ */
+
+.text
+.global test_sub64
+test_sub64:
+#ifdef CONFIG_32BIT
+	lw	a0, sub64
+#else
+	ld	a0, sub64
+#endif
+	addi	a0, a0, -32
+	ret
+first:
+	.space 32
+second:
+
+.data
+sub64:
+	.reloc		sub64, R_RISCV_ADD64, second
+	.reloc		sub64, R_RISCV_SUB64, first
+	.word		0
+	.word		0