arm/imx: fix power button on imx51 babbage board

Since commit 6571534b (plat-mxc: iomux-v3.h: implicitly enable
pull-up/down when that's desired) was in, the power button on imx51
babbage board stopped working because it's pulled up by mistake.
The patch removes the pull-up setting from the pad configuration for
that gpio to make the power button back to work.
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>

arch/arm/mach-mx5/board-mx51_babbage.c

@@ -362,7 +362,7 @@ static void __init mx51_babbage_init(void)
 {
 	iomux_v3_cfg_t usbh1stp = MX51_PAD_USBH1_STP__USBH1_STP;
 	iomux_v3_cfg_t power_key = NEW_PAD_CTRL(MX51_PAD_EIM_A27__GPIO2_21,
-		PAD_CTL_SRE_FAST | PAD_CTL_DSE_HIGH | PAD_CTL_PUS_100K_UP);
+		PAD_CTL_SRE_FAST | PAD_CTL_DSE_HIGH);
 
 	imx51_soc_init();