[PATCH] usb: xhci: remove the code build warning

[Dongjiu Geng]

Initialize the 'err' variate to remove the build warning,
the warning is shown as below:

drivers/usb/host/xhci-tegra.c: In function ‘tegra_xusb_mbox_thread’:
drivers/usb/host/xhci-tegra.c:552:6: warning: ‘err’ may be used uninitialized 
in this function [-Wuninitialized]
drivers/usb/host/xhci-tegra.c:482:6: note: ‘err’ was declared here

Signed-off-by: Dongjiu Geng <gengdong...@huawei.com>
---
How to reproduce:
1. make defconfig ARCH=arm
2. make -j100 CROSS_COMPILE=arm-linux-gnueabi- ARCH=arm

Then you can see below warnings:
drivers/usb/host/xhci-tegra.c: In function ‘tegra_xusb_mbox_thread’:
drivers/usb/host/xhci-tegra.c:552:6: warning: ‘err’ may be used uninitialized 
in this function [-Wuninitialized]
drivers/usb/host/xhci-tegra.c:482:6: note: ‘err’ was declared here
---
 drivers/usb/host/xhci-tegra.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c
index 2c076ea..1ed87ce 100644
--- a/drivers/usb/host/xhci-tegra.c
+++ b/drivers/usb/host/xhci-tegra.c
@@ -479,7 +479,7 @@ static void tegra_xusb_mbox_handle(struct tegra_xusb *tegra,
        unsigned long mask;
        unsigned int port;
        bool idle, enable;
-       int err;
+       int err = 0;
 
        memset(&rsp, 0, sizeof(rsp));
 
-- 
2.7.4