xhci: fix dma mask setup in xhci.c

The function dma_set_mask() tests internally whether the dma_mask pointer
for the device is initialized and fails if the dma_mask pointer is NULL.
On pci platforms, the device dma_mask pointer is initialized, when pci
devices are enumerated, to point to the pci_dev->dma_mask which is 0xffffffff.
However, for non-pci platforms, the dma_mask pointer may not be initialized
and in that case dma_set_mask() will fail.

This patch initializes the dma_mask and the coherent_dma_mask to 32bits
in xhci_plat_probe(), before the call to usb_create_hcd() that sets the
"uses_dma" flag for the usb bus and the call to usb_add_hcd() that creates
coherent dma pools for the usb hcd.

Moreover, a call to dma_set_mask() does not set the device coherent_dma_mask.
Since the xhci-hcd driver calls dma_alloc_coherent() and dma_pool_alloc()
to allocate consistent DMA memory blocks, the coherent DMA address mask
has to be set explicitly.

This patch sets the coherent_dma_mask to 64bits in xhci_gen_setup() when
the xHC is capable for 64-bit DMA addressing.

If dma_set_mask() succeeds, for a given bitmask, it is guaranteed that
the given bitmask is also supported for consistent DMA mappings.

Other changes introduced in this patch are:

- The return value of dma_set_mask() is checked to ensure that the required
  dma bitmask conforms with the host system's addressing capabilities.

- The dma_mask setup code for the non-primary hcd was removed since both
  primary and non-primary hcd refer to the same generic device whose
  dma_mask and coherent_dma_mask are already set during the setup of
  the primary hcd.

- The code for reading the HCCPARAMS register to find out the addressing
  capabilities of xHC was removed since its value is already cached in
  xhci->hccparams.

- hcd->self.controller was replaced with the dev variable since it is
  already available.

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>