drivers/mtd/nand: Move conditional compilation to Makefile

board/delta/nand.c

board/esd/common/auto_update.c

board/netta/netta.c

common/cmd_jffs2.c

common/cmd_nand.c

cpu/arm920t/s3c24x0/nand.c

cpu/arm926ejs/davinci/nand.c

cpu/ppc4xx/ndfc.c

doc/README.nand

drivers/mtd/nand/Makefile

drivers/mtd/nand/diskonchip.c

drivers/mtd/nand/fsl_upm.c

drivers/mtd/nand/nand.c

drivers/mtd/nand/nand_base.c

drivers/mtd/nand/nand_bbt.c

drivers/mtd/nand/nand_ecc.c

drivers/mtd/nand/nand_ids.c

drivers/mtd/nand/nand_util.c

drivers/mtd/nand_legacy/nand_legacy.c

fs/jffs2/jffs2_1pass.c