uboot-imx

mtdparts: fix usecount bug

add missing put_mtd_device, so mtd->usecount gets correct
decremented in get_mtd_info().

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Scott Wood <scottwood@freescale.com>
Cc: Tom Rini <trini@ti.com>