xhci: check for failed dma pool allocation

Fail and free the container context in case dma_pool_alloc() can't allocate
the raw context data part of it

This patch should be backported to kernels as old as 2.6.31, that
contain the commit d115b048 "USB: xhci:
Support for 64-byte contexts".

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: John Youn <johnyoun@synopsys.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>