usb: dwc2: call dwc2_is_controller_alive() under spinlock

This patch fixes the following problem: data transmission in direction
IN break unless the GSNPSID register access is done with spinlock held.
This issue occurs at least in Exynos4412 SoC, probably in many SoC's
from Exynos familly.

The problem is described here:
https://lkml.org/lkml/2014/12/22/185
And there is linux mailing list discussion:
https://lkml.org/lkml/2015/1/14/17

Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc2/core_intr.c

@@ -476,13 +476,13 @@ irqreturn_t dwc2_handle_common_intr(int irq, void *dev)
 	u32 gintsts;
 	irqreturn_t retval = IRQ_NONE;
 
+	spin_lock(&hsotg->lock);
+
 	if (!dwc2_is_controller_alive(hsotg)) {
 		dev_warn(hsotg->dev, "Controller is dead\n");
 		goto out;
 	}
 
-	spin_lock(&hsotg->lock);
-
 	gintsts = dwc2_read_common_intr(hsotg);
 	if (gintsts & ~GINTSTS_PRTINT)
 		retval = IRQ_HANDLED;
@@ -515,8 +515,8 @@ irqreturn_t dwc2_handle_common_intr(int irq, void *dev)
 		}
 	}
 
-	spin_unlock(&hsotg->lock);
 out:
+	spin_unlock(&hsotg->lock);
 	return retval;
 }
 EXPORT_SYMBOL_GPL(dwc2_handle_common_intr);