Especially functions that *set* TMR'ed variables *must* use it,
otherwise they only set one of the three copies, which makes the data
invalid.

When a bus error happened, the I2C peripheral's error bit remained
set. This caused it to respond erroneously in future transactions.

Now, when a bus error occurs, we're clearing the error bit and setting
the error flags in the STATUS_BYTE and STATUS_CML PMBus registers.
After the user reads those registers (using commands 0x78 and 0x7E),
their error flags are cleared.

The uC symbol was updated in the library: the (visible) difference is
that the thermal pad that was erroneously placed in the symbol while
physically missing from the package has been removed. Thus, the N/C
that was placed there is now hanging.