doc: Add documentation for using native_posix USB driver
doc: Add documentation for using native_posix USB driver

Add docs for using virtual native_posix USB controller over USB/IP
protocol.

Signed-off-by: Andrei Emeltchenko <a6565233ddc88e4fb9c66c1d70743223493f2ed4@intel.com>

zephyrproject-rtos/zephyr,finikorg/zephyr,ldts/zephyr,Vudentz/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,ldts/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,Vudentz/zephyr,ldts/zephyr,galak/zephyr,explora26/zephyr,Vudentz/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,nashif/zephyr,finikorg/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr