xhci: guard accesses to ep_state in xhci_endpoint_reset()

xhci: guard accesses to ep_state in xhci_endpoint_reset()

See https://github.com/raspberrypi/linux/issues/3981

Two read-modify-write cycles on ep->ep_state are not guarded by
xhci->lock. Fix these.

Fixes: f5249461b504 ("xhci: Clear the host side toggle manually when endpoint is soft reset")
Cc: stable@vger.kernel.org
Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20211008092547.3996295-2-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>