i2c: designware: Convert driver to using regmap API
Seeing the DW I2C driver is using flags-based accessors with two conditional clauses it would be better to replace them with the regmap API IO methods and to initialize the regmap object with read/write callbacks specific to the controller registers map implementation. This will be also handy for the drivers with non-standard registers mapping (like an embedded into the Baikal-T1 System Controller DW I2C block, which glue-driver is a part of this series). As before the driver tries to detect the mapping setup at probe stage and creates a regmap object accordingly, which will be used by the rest of the code to correctly access the controller registers. In two places it was appropriate to convert the hand-written read-modify-write and read-poll-loop design patterns to the corresponding regmap API ready-to-use methods. Note the regmap IO methods return value is checked only at the probe stage. The rest of the code won't do this because basically we have MMIO-based regmap so non of the read/write methods can fail (this also won't be needed for the Baikal-T1-specific I2C controller). Suggested-by:Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: