oxnas: clean-up NAND driver to fix probing issue

A re-write of the driver based on xway_nand.c and constants as
well as the cmd_ctrl() function from the original oxnas_nand.c
resulted in a extremely similar looking file (see diffsize),
and fixes the issue of NAND not being detected on newer kernels.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

SVN-Revision: 48986