xhci: Fix incorrect EP_STATE_MASK

EP_STATE_MASK should be 0x7 instead of 0xf

xhci spec 6.2.3 shows that the EP state field in the endpoint context data
structure consist of bits [2:0].
The old value included a bit from the next field which fortunately is a
 RsvdZ region. So hopefully this hasn't caused too much harm

Cc: stable@vger.kernel.org
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20200624135949.22611-2-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>