powerpc: Make test_translate_branch() independent of instruction length

test_translate_branch() uses two pointers to instructions within a
buffer, p and q, to test patch_branch(). The pointer arithmetic done on
them assumes a size of 4. This will not work if the instruction length
changes. Instead do the arithmetic relative to the void * to the buffer.
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Alistair Popple <alistair@popple.id.au>
Link: https://lore.kernel.org/r/20200506034050.24806-21-jniethe5@gmail.com

arch/powerpc/lib/code-patching.c

@@ -572,7 +572,7 @@ static void __init test_branch_bform(void)
 static void __init test_translate_branch(void)
 {
 	unsigned long addr;
-	struct ppc_inst *p, *q;
+	void *p, *q;
 	struct ppc_inst instr;
 	void *buf;
 
@@ -586,7 +586,7 @@ static void __init test_translate_branch(void)
 	addr = (unsigned long)p;
 	patch_branch(p, addr, 0);
 	check(instr_is_branch_to_addr(p, addr));
-	q = p + 1;
+	q = p + 4;
 	translate_branch(&instr, q, p);
 	patch_instruction(q, instr);
 	check(instr_is_branch_to_addr(q, addr));
@@ -642,7 +642,7 @@ static void __init test_translate_branch(void)
 	create_cond_branch(&instr, p, addr, 0);
 	patch_instruction(p, instr);
 	check(instr_is_branch_to_addr(p, addr));
-	q = p + 1;
+	q = buf + 4;
 	translate_branch(&instr, q, p);
 	patch_instruction(q, instr);
 	check(instr_is_branch_to_addr(q, addr));