Bugfixes noted by checking the code against the controller
documentation (TI document number SPRUE21):

 - Remove declarations for eight non-existent registers (!);
   and remove accesses to two of them.

 - Remove access to various non-existent bitfields in some of
   the registers which *do* exist (those fields must-be-zero).

 - Provide comment to replace bogus reset logic (removed above,
   it relied on non-existent bitfields).  Resets require GPIO
   help; this driver doesn't currently know about that.

With some minor cleanup:  relocate a comment, avoid an extra
lookup of the PIO timings.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>