Rearrange the imx274_start_<N> register tables to better match the
datasheet and slightly simplify code:
- collapes tables 1 and 2, they are applied one after each other and
together they implement the fixed part 1 of the startup procedure
in the datasheet
- while there, cleanup comments
- rename tables 3 and 4 -> 2 and 3, coherently with the datasheet