commit 69daf75a upstream.

First check for rate == 0 in set_rate and round_rate to avoid div by zero.
Then, in order to get the closest rate, round all divisions to the closest
result instead of rounding them down.
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Michael Turquette <mturquette@linaro.org>
[ luis: 3.16 prereq for:
  45912431 "clk: at91: usb: propagate rate modification to the parent clk" ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>