ACPICA: Add macros to extract flag bits from resource descriptors.

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: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>