update ekf

[ChristophTobler]

This PR includes the fix of #8102 and it uses the ground clearance parameter if the vehicle is on ground and out of range.

[priseborough]

The code changes look OK, but the following mavros regression test failed:

http://sitl01.dronetest.io/job/PX4%20Firmware%20POSIX%20SITL%20PRs/7196/testReport/__main__/MavrosMissionTest/test_mission/

[ChristophTobler]

There seem to be some issues with CI. Now sitl worked but travis didn't even though I didn't change anything... And semaphoreci is broken for a while it seems.

[dagar]

The semaphoreci failure is real. px4fmu-v2_default is out of flash again.

@davids5 can we remove mpu9250 from px4fmu-v2_default?

[ChristophTobler]

@priseborough @dagar I've rebased this PR and now all checks have passed.

[dagar]

Good to go?

[dagar]

This is a bit picky, but on the Firmware side we should try to use the BlockParam interface for const access. _rng_gnd_clearance.get()
There's a mix of usage in ekf2_main so we can update them all later in a separate pass.

[priseborough]

Can we bump the ecl reference to 61e0c04 so that it includes the position timeout bugfix?

[ChristophTobler]

Two test flights:
https://logs.px4.io/plot_app?log=0ec0d863-a41e-4594-8966-34b6f6465dcb
https://logs.px4.io/plot_app?log=7b9d66a9-8ed6-4f7b-abea-8361010d4f0a (with range aid)

Was working nicely! I also switched from flow to GPS + flow and back.
The only thing is that it is saying ekf2 and frsky_telemetry are low on stack (see log).

[LorenzMeier]

Awesome!

[priseborough]

I've started on protection against flying the flow sensor outside of its speed and minimum focus distance here: https://github.com/PX4/ecl/tree/ekfPosCtrlLimits-wip and here: https://github.com/priseborough/Firmware/tree/ekfPosCtrlLimits-wip

I will submit a PR for these changes tomorrow. i did some testing today, but it was too windy to make a useful assessment. It works in SITL, but the controller changes need to be flown manually to get a better assessment as to whether the method of respecting the minimum height and max speed is acceptable from a UX point of view.