media: cec: fix smatch error

drivers/media/cec/cec-pin-error-inj.c:231
cec_pin_error_inj_parse_line() error: uninitialized symbol 'pos'.

The tx-add-bytes command didn't check for the presence of an argument, and
also didn't check that it was > 0.

This should fix this error.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/cec/cec-pin-error-inj.c

@@ -203,16 +203,18 @@ bool cec_pin_error_inj_parse_line(struct cec_adapter *adap, char *line)
 		mode_mask = CEC_ERROR_INJ_MODE_MASK << mode_offset;
 		arg_idx = cec_error_inj_cmds[i].arg_idx;
 
-		if (mode_offset == CEC_ERROR_INJ_RX_ARB_LOST_OFFSET ||
-		    mode_offset == CEC_ERROR_INJ_TX_ADD_BYTES_OFFSET)
-			is_bit_pos = false;
-
 		if (mode_offset == CEC_ERROR_INJ_RX_ARB_LOST_OFFSET) {
 			if (has_op)
 				return false;
 			if (!has_pos)
 				pos = 0x0f;
+			is_bit_pos = false;
+		} else if (mode_offset == CEC_ERROR_INJ_TX_ADD_BYTES_OFFSET) {
+			if (!has_pos || !pos)
+				return false;
+			is_bit_pos = false;
 		}
+
 		if (arg_idx >= 0 && is_bit_pos) {
 			if (!has_pos || pos >= 160)
 				return false;