[ARM] pxa/corgi: use leds-gpio for led driving and drop leds-corgi

Now as the scoop pins are covered by the generic gpio API,
we can use leds-gpio driver instead of special leds-corgi

Drop leds-corgi.c and remove the declaration of now un-referenced
corgiscoop_device.

Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Eric Miao <eric.miao@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>