Minor tweaks:

  - Bugfix handling of EVENTQ_DEFAULT ... recognize it, and
    implement as EVENTQ_1 instead of reserved/illegal value

  - Use the defined enum type internally

  - Have MMC use TC1, as appropriate for "longer, nonreal-time
    sensitive transfers" (per docs) ... instead of using TC0,
    as for "urgent, small, real-time sensitive transfers".

Arguably, TC0 priority should be increased (to 0) to be
higher priority than the ARM ... matching "urgent" etc.

The added TCs on DM646x chips are still not recognized.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>