staging: comedi: ni_labpc: move register defs to new file

The new "ni_labpc_isadma" module will need to access some register
definitions from "ni_labpc.c", which is not part of the module's source.
Move all the register definitions into a new, common header file
"ni_labpc_regs.h".

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>