This removes in nand.h code that is verbatim duplicated from bbm.h,
including directly bbm.h in nand.h. The previous state of affairs
prevented compiling code for a board hosting both NAND and OneNAND chips.

Reported-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alessandro Rubini <rubini@unipv.it>
Signed-off-by: Scott Wood <scottwood@freescale.com>