usb: xhci: Add virt_to_phys() to support mapped platforms

Some platforms, like MIPS Octeon, use mapped addresses (virtual address
!= physical address). On these platforms we need to make sure, that the
local virtual addresses are converted to physical (DMA) addresses for
the xHCI controller. This patch adds the missing virt_to_phys() calls,
so that the correct addresses are used.

Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Marek Vasut <marex@denx.de>