eir: Fix incorrect eir_length() parsing

eir: Fix incorrect eir_length() parsing

Issue:
The COD value displayed via dbus during inquiry is wrong.
This is because of the incorrect return length of the eir_length(),
which leads to appending the COD at wrong location.

Analysis:
After appending the COD at the end of the eir data, we can see
there are some '00' present in the eir field length in the eir file.
XX:XX:XX:XX:XX:XX 07095359414D5043020A040B0312111F110C110E110311
0000000000000000000000040D000142

Fix:
Corrected the length calculation in eir_length(), which is determining,
which position the COD should append