Moves commands into nand/tcl.c and core implementation to 'nand/core.c'
and 'nand/fileio.c'. Eliminates 'flash/nand.c'.
Adds 'nand/imp.h' to share routines between TCL commands and core.
This work parallels the NOR directory, encapsulating the NAND drivers
into a separate file. This takes an extra step by encapsulating the
type of data structure used to manage the drivers, allowing it to be
changed from an array to a dynamic list in the future.
Includes the src directory in the search path, so header files may be
migrated from:
#include "foo.h"
to
#include <module/foo.h>
which is more conducive for installation.
