ARM: OMAP2+: Convert NAND to use gpmc_cs_program_settings()

Convert the OMAP2+ NAND code to use the gpmc_cs_program_settings()
function for configuring the various GPMC options instead of directly
programming the CONFIG1 register.

This moves the configuration of some GPMC options outside the
nand_gpmc_retime() because these options should only need to be set once
regardless of whether the gpmc timing is changing dynamically at runtime.
The programming of where the wait-pin is also moved slightly, but this
will not have any impact to existing devices as no boards are currently
setting the dev_ready variable.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>