omap3: IGEP v2: Improve igep2_flash_init() function

The changes are:
  - Use 'for' loop instead 'while' loop.
  - No need to initialize ret to 0, we're assigning it right after.
  - No need to check for onenandcs < GPMC_CS_NUM here, it will always be true.

Signed-off-by: Enric Balletbo i Serra <eballetbo@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>