i2c: designware: refactoring of the i2c-designware

- Factor out all _master() part of code from i2c-designware-core
  and i2c-designware-platdrv to separate functions.
- Standardize all code related with MASTER mode.
- I have to take off DW_IC_INTR_TX_EMPTY from DW_IC_INTR_DEFAULT_MASK
  because it is master specific.

The purpose of this is to prepare the controller to have is I2C MASTER
flow in a separate driver. To do this first all the
functions/definitions related to the MASTER flow were identified.

Signed-off-by: Luis Oliveira <lolivei@synopsys.com>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>