The OMAP GPMC module has certain registers dedicated for NAND
access and some NAND bits mixed with other GPMC functionality.

For the NAND dedicated registers we have the struct gpmc_nand_regs.

The NAND driver needs to access NAND specific bits from the
following non-dedicated registers
- EMPTYWRITEBUFFERSTATUS from GPMC_STATUS

For accessing these bits we introduce the struct gpmc_nand_ops.

Add gpmc_omap_get_nand_ops() that returns the gpmc_nand_ops along
with updating the gpmc_nand_regs. This API will be called by the
OMAP NAND driver to access the necessary bits in GPMC register space.
Signed-off-by: Roger Quadros <rogerq@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>