This is a minor cleanup of dm6446 evm NAND configuration:

 - Move pinmux from NAND driver to the board setup code where it belongs.
 - Use of NAND is unrelated to VLYNQ and AEAW; don't enable them.
 - Move IDE pinmux out of clock configuration to board setup.
 - The conflict for IDE with *any* other EMIF user, not just NOR;
   so don't always configure IDE, NAND, and NOR.

The IDE config should maybe move to the new dm644x.c file, but the
flash configuration is very board-specific.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>