libusb_set_options: Adjust semantics of libusb_set_option for log level

This commit updates the actual semantics of:

libusb_set_option(_, LIBUSB_OPTION_LOG_LEVEL, _)

to match the documentation. The documentation states that if the
LIBUSB_DEBUG environment variable is set then that level overrides the
value set by libusb_set_option.

Signed-off-by: Nathan Hjelm <hjelmn@google.com>
2 files changed