usb: xhci-mtk: use dma_set_mask_and_coherent() in probe function

This patch uses the simpler dma_set_mask_and_coherent() instead of
doing these as separate steps

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>