USB: ftdi_sio: fix resolution of 2232H baud rate dividers

The 2232H high speed baud rates also support fractional baud
rate divisors, but when the performing the divisions before
the multiplication, the fractional bits are lost.

Signed-off-by: Daniel Glöckner <dg@emlix.com>
Acked-by: Mark Adamson <mark.adamson@ftdichip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>