xhci: Bigendian fix for xhci_check_bandwidth()

Commit 834cb0fc "xhci: Fix memory leak
bug when dropping endpoints" added a small endian bug.  This patch fixes
xhci_check_bandwidth() to read add/drop_flags LE.

Signed-off-by: Matt Evans <matt@ozlabs.org>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>