musb_hdrc, CamelCase begone (cppi descriptors, ...)

More CamelCase removal from the CPPI support.  In this case:

 - CPPI descriptor members;
 - Some members of the controller struct;
 - Rename "regBase" variables (as "tibase", vs Mentor registers)
 - Rename otgCh variables as cppi_ch;

This code still has a bunch of CaMeLcAsInG going on.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>