[MTD] [NAND] fix nandsim sched.h references

Fix sched.h references:

build-r7149.out:/local/linsrc/linux-next-20081215/drivers/mtd/nand/nandsim.c:1326: error: dereferencing pointer to incomplete type
build-r7149.out:/local/linsrc/linux-next-20081215/drivers/mtd/nand/nandsim.c:1326: error: 'PF_MEMALLOC' undeclared (first use in this function)
build-r7149.out:/local/linsrc/linux-next-20081215/drivers/mtd/nand/nandsim.c:1328: error: dereferencing pointer to incomplete type
build-r7149.out:/local/linsrc/linux-next-20081215/drivers/mtd/nand/nandsim.c:1335: error: dereferencing pointer to incomplete type
build-r7149.out:/local/linsrc/linux-next-20081215/drivers/mtd/nand/nandsim.c:1335: error: 'PF_MEMALLOC' undeclared (first use in this function)
build-r7149.out:make[4]: *** [drivers/mtd/nand/nandsim.o] Error 1

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>