usb: dwc3: replace hard-coded constant in DWC3_GCTL_SCALEDOWN(3)

Define DWC3_GCTL_SCALEDOWN_MASK and use it in place of
DWC3_GCTL_SCALEDOWN(3).
Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/core.c

@@ -350,7 +350,7 @@ static int __devinit dwc3_core_init(struct dwc3 *dwc)
 	dwc3_cache_hwparams(dwc);
 
 	reg = dwc3_readl(dwc->regs, DWC3_GCTL);
-	reg &= ~DWC3_GCTL_SCALEDOWN(3);
+	reg &= ~DWC3_GCTL_SCALEDOWN_MASK;
 	reg &= ~DWC3_GCTL_DISSCRAMBLE;
 
 	switch (DWC3_GHWPARAMS1_EN_PWROPT(dwc->hwparams.hwparams1)) {

drivers/usb/dwc3/core.h

@@ -161,6 +161,7 @@
 
 #define DWC3_GCTL_CORESOFTRESET	(1 << 11)
 #define DWC3_GCTL_SCALEDOWN(n)	((n) << 4)
+#define DWC3_GCTL_SCALEDOWN_MASK DWC3_GCTL_SCALEDOWN(3)
 #define DWC3_GCTL_DISSCRAMBLE	(1 << 3)
 #define DWC3_GCTL_DSBLCLKGTNG	(1 << 0)