ARM: tegra: powergate: Don't error out if new state == old state

Don't treat it as an error if a partition is already in the same power
state when a user wants to power it on or off. This allows code to
proceed if no state change is required.

Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Stephen Warren <swarren@nvidia.com>

arch/arm/mach-tegra/powergate.c

@@ -76,7 +76,7 @@ static int tegra_powergate_set(int id, bool new_state)
 
 	if (status == new_state) {
 		spin_unlock_irqrestore(&tegra_powergate_lock, flags);
-		return -EINVAL;
+		return 0;
 	}
 
 	pmc_write(PWRGATE_TOGGLE_START | id, PWRGATE_TOGGLE);