clk: multiplier: Prevent the multiplier from under / over flowing

clk: multiplier: Prevent the multiplier from under / over flowing

commit 25f77a3aa4cb948666bf8e7fd972533ea487c3bd upstream.

In the current multiplier base clock implementation, if the
CLK_SET_RATE_PARENT flag isn't set, the code will not make sure that the
multiplier computed remains within the boundaries of our clock.

This means that if the clock we want to reach is below the parent rate,
or if the multiplier is above the maximum that we can reach, we will end up
with a completely bogus one that the clock cannot achieve.

Fixes: f2e0a53271a4 ("clk: Add a basic multiplier clock")
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/1463402840-17062-3-git-send-email-maxime.ripard@free-electrons.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>