Fix nandsim build error, missing #include:

linux-next-20080605/drivers/mtd/nand/nandsim.c: In function 'divide':
linux-next-20080605/drivers/mtd/nand/nandsim.c:462: error: implicit declaration of function 'do_div'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>