package/usb_modeswitch: drop unicode space in comment

Commit "a554109a package/usb_modeswitch: disable parallel build" added
a unicode space in a comment. Replace it with a normal ASCII space for
consistency with elsewhere.

Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>