DCP405: With 'Best' current scaling, allow using 5 uA steps while in low current range

[Cat-Ion]

When the current scaling is set to 'Best' and the current is <50 mA, rotating the encoder uses 0.5 mA steps, while 5 uA steps should be possible.

[prasimix]

Possible problem here is that at the beginning of the scale change will be very slow, and you have to make few turn to first reach 50 mA and to come into position to have more responsive encoder.

[prasimix]

If set current is 50 mA or less when change current range from Best to High, it keeps to use uA instead of mA to display when load is not connected. OE state recycling is needed to use mA.

[prasimix]

Fixed