i2c: designware: Switch header to use BIT() and GENMASK()

Currently header file uses partially BIT() and GENMASK() macros.
Switch it to use those macros in all cases where it's applicable
for the sake of consistency.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>