【mc_att_control】 Remove unnecessary defaults.

[xdwgood]

😃 I don't think we need this extra variable.　https://github.com/PX4/Firmware/blob/master/src/modules/mc_att_control/mc_att_control_main.cpp#L95　
This variable ATTITUDE_TC_DEFAULT　is used to adjust the pid.　
Use it here:　https://github.com/PX4/Firmware/blob/master/src/modules/mc_att_control/mc_att_control_main.cpp#L534
I think we can use this parameter MC_ROLL_TC　to directly adjust the pid.　https://github.com/PX4/Firmware/blob/master/src/modules/mc_att_control/mc_att_control_params.c#L54
It is also a mistake to follow the current logic.　https://github.com/PX4/Firmware/blob/master/src/modules/mc_att_control/mc_att_control_params.c#L45
Should : Increase if the system is too twitchy, Reduce if the response is too slow and sluggish.

@MaEtUgR @Stifael Do I understand that correctly?　:rabbit2:

[MaEtUgR]

@xdwgood Don't use the TC parameters, I just recently requested to take them out: a349bd8
It will likely get merged soon.

TC stands for time constant. It just the inverse of a gain -> K = 1/TC
In this implementation it was multiplied to the gain as GAIN * 0.2/TC which means if you stay on default parameters (which is 0.2) it multiplies by 1 and has no effect.
If you changed the parameter you blindly rescale the gains of rate and attitude control loop... which makes no sense from a control perspective and only generates confusion in my opinion. That's why I deleted them.