Currently, USB Host unit tests that require a software triggered disconnection/
reconnection rely on the 'usb_phy_action()' function.
This commit replaces those calls with 'hcd_port_command()' or
'usb_host_lib_set_root_port_power()'.
Note: Also removed 'test_usb_common.h/c' as it is no longer necessary are the
function call replacements.
