Update submodule ecl to latest Wed Aug 26 00:38:38 UTC 2020

    - ecl in PX4/Firmware (97758b7): PX4/PX4-ECL@bd0c5fb
    - ecl current upstream: PX4/PX4-ECL@4872f2a
    - Changes: PX4/PX4-ECL@bd0c5fb...4872f2a

    4872f2a 2020-08-15 Kamil Ritz - Remove not used code
0fafd4d 2020-08-15 Kamil Ritz - precompute cos and sin of yaw once before mutliple use
114516b 2020-08-15 Kamil Ritz - Use new added matrix functions
1f637af 2020-08-15 Kamil Ritz - Add const modifier
aa2c77f 2020-08-22 kamilritz - Small cleanup in velposfusion
644e903 2020-08-22 kamilritz - Apply measurementUpdate function
404edde 2020-08-22 kamilritz - Add measurementUpdate function
f6252ff 2020-08-22 kamilritz - small cleanup  in limitDeclination
f62662e 2020-08-21 Daniel Agar - update change_indication for newer WMM tables
802a6d9 2020-08-21 PX4 BuildBot - Update geo_lookup WMM  to latest Fri Aug 21 11:48:14 UTC 2020