mtd: omap2: correct 'info' pointer in 'omap_nand_remove'

Removing OMAP NAND driver, when loaded as a module, gives error and
does not get success. This fixes this and makes driver loadable and
removable run time.

Signed-off-by: Vimal Singh <vimalsingh@ti.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>