usb_master: Use libusb_host_ctx when scanning for devices
usb_master: Use libusb_host_ctx when scanning for devices

struct qiprog_context.libusb_host_ctx is passed to libusb_init()
in qiprog_init() and the same context must be passed also to
libusb_get_device_list() when scanning for devices in usb_master.c.

Signed-off-by: Peter Stuge <4b8373d016f277527198385ba72fda0feb5da015@stuge.se>

mrnuke/qiprog