ARM: plat-orion: make gpiochip label unique

The former implementation adds a fix gpiochip label string
to the framework. This is confusing because orion_gpio_init
is called more than once and this ends up in different gpiochips
with the same label.

This patch adds the already present orion_gpio_chip_count to the
label string to make it unique in the system.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Cc: Lennert Buytenhek <kernel@wantstofly.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>