memory: omap-gpmc: Move gpio functions out of #ifdef CONFIG_OF

The gpio related functions were mistakenly built only if CONFIG_OF
is defined. They are needed even otherwise and will cause build
failures if CONFIG_OF is not defined. Move the gpio functions
outside #ifdef CONFIG_OF.

Fixes: d2d00862 ("memory: omap-gpmc: Support general purpose input for WAITPINs")

Signed-off-by: Roger Quadros <rogerq@ti.com>