More cleanup:

 - We don't actually need "dma_chan[X].param_no", since we can
   always write "X" instead.  Remove "param_no".

 - That means dma_chan[] itself can go.  Yay!

 - A few more arrays can be __initconst.

 - Comment updates:  make the top look normal, add section markers.

 - Stop using that typedef internally.

 - Sanity checked #defines for edmacc_param.opt:  remove three bits
   that are reserved/zero in documentation, line up the others.

Except for the "in use" bitmask and the IRQ callback data, there
doesn't need to be much DMA driver state outside of EDMA registers
and parameter RAM.

Saves about 700 bytes of space, mostly data.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>