using SPI probing

we need to check on every sample at the full rate

this saves us one mag slot for another external mag, and leaves the
primary MPU9250 undisturbed by the mag traffic on the bus

not called from frontend

this makes booting a PH2 without its sensor hat on much easier

make sure fifo reset doesn't check I2C master enable

check temperature every 255 samples against FIFO data

this makes the 1P filter optionally syntax compatible with the 2P
filter and much more CPU efficient.

Drone Japan homework: input name and pull request.

Global: Aggregate the same definitions.

fixed warnings

Two cases of what seems to be FIFO alignment errors have been seen on
a Pixracer-beta board with a ICM-20608. At a cost of 2 extra bytes per
transfer we can catch these by looking for sudden temperature changes
caused by bad data in the temperature registers.

use zero sample rate divider on both MPU6000 and ICM20608

very slightly faster