pinctrl: at91: fix get_pullup/down function return

commit 05d3534a321d7fe4524b3b83bb20318282f3ec2c upstream.

In PIO_PUSR and PIO_PPDSR register if a given bit is set 1 this means the
pullup/down for this pin (pin is represented as a bit position) is
disabled.

Signed-off-by: Boris BREZILLON <b.brezillon@overkiz.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>