ARM: OMAP2+: Simplify code configuring ONENAND devices

The OMAP2+ code that configures the GPMC for ONENAND devices is copying
structures between functions unnecessarily. Avoid this by passing
pointers instead and simplify the code.

A pointer to structure "omap_onenand_platform_data" is passed to the
function omap2_onenand_calc_sync_timings(), but only the flags member
of the structure is used. Simplify the code by only passing the flags
member and not the entire structure.

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