... instead of an array index to a global array. This is
an intermediate step to make the drivers conform to
the new driver model.
This only changes from using a direct array index to using
device structs. The UARTs are still staticlly defined.
Later patches will make the drivers utilize the driver
initialization procedure specified by the driver model.
Change-Id: I18041bbb4b0efdf8ae87088fd000b391d0827e9b
Signed-off-by: Daniel Leung <daniel.leung@intel.com>