pinctrl: bcm2835: Use existing pointer to struct device

The pointer to "pdev->dev" is already stored in "dev", so use it in
devm_request_and_ioremap().

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>