ARM: plat-versatile: convert LEDs to platform device

The LEDs were initialized unconditionally with an fs_initcall()
which doesn't play well with multiplatform. Convert the driver
to a platform device and convert all boards with these LEDs
to register a platform device and pass the register as a
resource instead.

Tested successfully on the Versatile/AB and RealView PB1176.

Cc: Bryan Wu <cooloney@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Pawel Moll <pawel.moll@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>