[MTD] Make uclinux_mtd_cleanup and uclinux_mtd_init static

The functions uclinux_mtd_cleanup and uclinux_mtd_init do
not heed to be global. Add the needed keyword to the file
drivers/mtd/maps/uclinux.c to make these functions static.

Signed-off-by: Dmitri Vorobiev <dmitri.vorobiev@movial.fi>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>