video: sa1100fb: use devm_gpio_request_one()

Switch to using devm_gpio_request_one() to request the shannon gpio
and move the request before the video memory allocation, so we request
all device managed resources before this large allocation attempt.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>