powerpc/oprofile: fix potential buffer overrun in op_model_cell.c

Fix potential initial_lfsr buffer overrun.
Writing past the end of the buffer could happen when index == ENTRIES
Signed-off-by: Denis Kirjanov <dkirjanov@kernel.org>
Cc: stable@kernel.org
Signed-off-by: Robert Richter <robert.richter@amd.com>

arch/powerpc/oprofile/op_model_cell.c

@@ -1077,7 +1077,7 @@ static int calculate_lfsr(int n)
 		index = ENTRIES-1;
 
 	/* make sure index is valid */
-	if ((index > ENTRIES) || (index < 0))
+	if ((index >= ENTRIES) || (index < 0))
 		index = ENTRIES-1;
 
 	return initial_lfsr[index];