USB: serial: belkin_sa: Various needed fixes

Use the baud rate stuff from the kernel don't parse CBAUD directly
Remove pointless and wrong 'no change' check

Could do with some good testing as well but again better than adding &&
BROKEN

(The use of BELKIN_SA_BAUD() might seem a bit odd but x/a = b and x/b =
a (rounded for integers)).

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>