fbdev: amba: Link fb device to its parent

Some pieces of userspace like debian-installer expect to find the fb0
driver name by readlink-ing /sys/class/graphics/fb0/device/driver but
this was broken with amba-clcd as it sets up fb_info manually and missed
the .device parent pointer.

Signed-off-by: Loïc Minier <loic.minier@linaro.org>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>