usb: xhci: Increase xhci halt timeout

Currently, certain controllers with lower core clock rates, takes
more than 32ms to set the halted bit. This results in XHCI halt
timeout.
Fix this by increasing the timeout to 48ms.

Change-Id: I2f2715a11a947e01303c659e257ef0cabb311cac
Signed-off-by: Harsh Agarwal <harshq@codeaurora.org>