mtd: nand: omap2: Do not assign omap_nand_info to platform drvdata

commit 67ce04bf ("mtd: nand: add OMAP2/OMAP3 NAND driver") assigned
pointer to omap_nand_info to the platform drvdata in probe function
just to be reasigned later to the pointer to mtd_info, which is
what remove function expects it to be. Remove useless assignment.

Signed-off-by: Ladislav Michl <ladis@linux-mips.org>
Acked-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>