flash_erase: check the nand type

flash_erase: check the nand type

Now, the MTD_NANDFLASH stands for SLC nand, and the MTD_MLCNANDFLASH
stands for the MLC nand.

This patch includes the stdbool.h, and changes the "isNAND" to boolean type,
and checks the right nand type for the MLC and SLC nand.

If the user wants to format a MLC nand for JFFS2, we will print out a message
to warn him, and exit right now.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>