Improves readability and maintainability of the code.  Fixes a
problem with the UART serial bus descriptor for the number of
data bits flags (was incorrectly 2 bits, should be 3).
Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>