ARM: OMAP2+: gpmc-onenand: drop __init annotation

gpmc_onenand_init() will be called from another driver's probe() function,
so drop the __init annotation, in order to prevent section mismatches.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>