staging: most: hdm-usb: remove redundant spinlocks

This patch removes the spinlocks when accessing the usb_anchor list,
because the struct usb_anchor is using its own lock.

Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>