enhance the gyro calibration process

[kikoqiu]

Enhance the gyro calibration process to avoid false positvie signals of still, which sometimes causes the quad to flip on arm, because of the gyro bias.

commit 1

enhance sixaxis_wait_for_still to avoid false positive signals of still.
remove no-effect code for limit in sixaxis_gyro_cal.
pause gyro bias calibration when move is detected.

commit 2

implement MSP_ANALOG to enable DJI goggles osd voltage display.

[bkleiner]

We gonna have to have a discussion if we want to get rid of the limit. I will try to have a test asap.

[bkleiner]

Still want to test but otherwise looks good to me.

[kikoqiu]

Still want to test but otherwise looks good to me.

Of course it needs a test. My test is ok with the neutronrc 2s aio. Maybe it needs a test on another board.