darwin/libusb_reset: reenumerate device if the device descriptor or any configuration...

darwin/libusb_reset: reenumerate device if the device descriptor or any configuration descriptor has changed

Some background: the Linux kernel causes a device to be reenumeration when
reset if the device's descriptors have changed. Darwin does not provide
this feature but instead provides a call to force the reenumeration of
a device. This behavior is required to support the firmware update
protocol used by some devices.

This patch updates darwin_reset to check if either the device or
configuration descriptors have changed. If they have darwin_reset will
ask the OS to reenumerate the device and return LIBUSB_ERROR_NOT_FOUND
or LIBUSB_SUCCESS accordingly.

Fixes #169

Signed-off-by: Hans de Goede <hdegoede@redhat.com>