amba: tegra-ahb: Fix device leak on SMMU enable

commit 500e136 upstream.

Make sure to drop the reference taken to the AHB platform device when
looking up its driver data while enabling the SMMU.

Note that holding a reference to a device does not prevent its driver
data from going away.

Fixes: 89c788b ("ARM: tegra: Add SMMU enabler in AHB")
Cc: stable@vger.kernel.org	# 3.5
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: jhovold

drivers/amba/tegra-ahb.c

@@ -144,6 +144,7 @@ int tegra_ahb_enable_smmu(struct device_node *dn)
 	if (!dev)
 		return -EPROBE_DEFER;
 	ahb = dev_get_drvdata(dev);
+	put_device(dev);
 	val = gizmo_readl(ahb, AHB_ARBITRATION_XBAR_CTRL);
 	val |= AHB_ARBITRATION_XBAR_CTRL_SMMU_INIT_DONE;
 	gizmo_writel(ahb, val, AHB_ARBITRATION_XBAR_CTRL);