drivers/w1: driver for ds2485 1-Wire master

This commit introduces the 1-wire master driver for maxim ds2485.

The ds2485 master has nearly the same (1-wire) feature set and
i2c-interface as the ds2477.
Therefore the common parts are extracted, but to avoid
any nda troubles only the ds2485 specific part is included.

Compared to older 1-wire masters, the ds2485 supports higher level
commands, supporting multi byte operations, search next, automatic crc
calculation.

In this driver only basic read and write operations are supported,
further hardware features are not yet utilized by the driver.

Signed-off-by: Thomas Stranger <thomas.stranger@outlook.com>