memory: tegra20-mc: Fix hang in IRQ handler.

In Tegra20 any memory controller interrupt would cause an
infinite loop in the IRQ handler.
Signed-off-by: NTuomas Tynkkynen <ttynkkynen@nvidia.com>
Reviewed-by: NStephen Warren <swarren@nvidia.com>
Reviewed-by: NThierry Reding <thierry.reding@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/memory/tegra20-mc.c

@@ -193,8 +193,11 @@ static irqreturn_t tegra20_mc_isr(int irq, void *data)
 	mask &= stat;
 	if (!mask)
 		return IRQ_NONE;
-	while ((bit = ffs(mask)) != 0)
+	while ((bit = ffs(mask)) != 0) {
 		tegra20_mc_decode(mc, bit - 1);
+		mask &= ~BIT(bit - 1);
+	}
+
 	mc_writel(mc, stat, MC_INTSTATUS);
 	return IRQ_HANDLED;
 }