musb_hdrc, CamelCase begone (cppi struct, locals ...)

musb_hdrc, CamelCase begone (cppi struct, locals ...)

Even more CamelCase removal from CPPI:
 - members of cppi_channel struct
 - parameters to cppi_channel_program()
 - "buffSz" local variables
 - "chNum" local variables
 - "regVal" local variables

Also
 - remove the FIXME about using container_of(), that's resolved now
 - stop using the now-pointless private_data fields
 - remove the redundant actualLen field (use dma_channel.actual_len)
 - remove some redundent local variables

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