i2c: aspeed: fix build warning

Upstream commit 3e9efc32 ("i2c: aspeed: Handle master/slave combined irq events
properly") reworked the interrupt handling and fixed a warning in the process:

drivers/i2c/busses/i2c-aspeed.c: In function 'aspeed_i2c_bus_irq':
drivers/i2c/busses/i2c-aspeed.c:567:1: error: label 'out' defined but not used [-Werror=unused-label]

The warning is still present in v4.19.8 and can be fixed either by applying
that original patch, or by adding a simple #ifdef.

Here, I choose the second simpler option as the original patch seems too
invasive for a stable backport.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/i2c/busses/i2c-aspeed.c

@@ -555,7 +555,7 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
 	spin_lock(&bus->lock);
 
 #if IS_ENABLED(CONFIG_I2C_SLAVE)
-	if (aspeed_i2c_slave_irq(bus)) {
+	if (IS_ENABLED(CONFIG_I2C_SLAVE) && aspeed_i2c_slave_irq(bus)) {
 		dev_dbg(bus->dev, "irq handled by slave.\n");
 		ret = true;
 		goto out;
@@ -564,7 +564,9 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
 
 	ret = aspeed_i2c_master_irq(bus);
 
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
 out:
+#endif
 	spin_unlock(&bus->lock);
 	return ret ? IRQ_HANDLED : IRQ_NONE;
 }