ARM: OMAP1: ams-delta: convert latches to basic_mmio_gpio

Once ready, ams-delta specific device drivers currently calling custom
ams_delta_latch[12]_write() functions can be updated to call generic
gpio_set_value() instead, which will make them less platform dependent.
Even more, some custom ams-delta only drivers can perhaps be dropped
from the tree after converting selected ams-delta platform devices to
follow generic GPIO based device models.

The latch_gpios[] table is initially filled with all latch1 and latch2
GPIO pins in order to register and initialize them from the board file
until those are handled by respective existing device drivers (leds,
nand, lcd, serio, asoc, serial). That table will get almost empty after
the transision process is completed, holding only pins not used by any
drivers / connected to unused devices, in order to initialize them from
the board file for power saving purposes.

The new ams_delta_latch_write() function is a unified replacement for
those removed ams_delta_latch[12]_write(), and serves as a temporary
wrapper over gpio_set_value(), providing the old API for those not yet
updated device drivers, and will be removed after all custom drivers are
converted or replaced.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Signed-off-by: Tony Lindgren <tony@atomide.com>