USB: serial: ch341: put reset_resume callback back.

A few patches ago, I removed the reset_resume callback, changing it to
resume instead.  Now that the usb-serial core supports reset_resume, put
this driver callback back as well, so it should work identically to how
it was originally.

Now if this function really is doing what it should be doing, well,
that's a different story, but we are at least doing the identical thing
that we were before...

Cc: Johan Hovold <jhovold@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>