media: mxl692: remove impossible condition

Fix the following coverity warning:

This greater-than-or-equal-to-zero comparison of an unsigned value is
always true. "opcode >= 0".
Reported-by: NAbaci Robot <abaci@linux.alibaba.com>
Signed-off-by: NJiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: NSean Young <sean@mess.org>
Signed-off-by: NMauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/dvb-frontends/mxl692.c

@@ -377,7 +377,7 @@ static int mxl692_memread(struct mxl692_dev *dev, u32 addr,
 
 static const char *mxl692_opcode_string(u8 opcode)
 {
-	if (opcode >= 0 && opcode <= MXL_EAGLE_OPCODE_INTERNAL)
+	if (opcode <= MXL_EAGLE_OPCODE_INTERNAL)
 		return MXL_EAGLE_OPCODE_STRING[opcode];
 
 	return "invalid opcode";