staging: rtl8712: correct spelling mistake in comment

Correct a spelling mistake discovered by checkpatch.
attatch -> attach

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20200413215109.15749-1-straube.linux@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>