clk: bcm-2835: Pick the closest clock rate

The driver currently tries to pick the closest rate that is lower than
the rate being requested.

This causes an issue with clk_set_min_rate() since it actively checks
for the rounded rate to be above the minimum that was just set.

Let's change the logic a bit to pick the closest rate to the requested
rate, no matter if it's actually higher or lower.

Fixes: 6d18b8ad ("clk: bcm2835: Support for clock parent selection")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenz@kernel.org>
Tested-by: Nicolas Saenz Julienne <nsaenz@kernel.org> # boot and basic functionality
Tested-by: Michael Stapelberg <michael@stapelberg.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210922125419.4125779-2-maxime@cerno.tech

drivers/clk/bcm/clk-bcm2835.c

@@ -1216,7 +1216,7 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
 		rate = bcm2835_clock_choose_div_and_prate(hw, i, req->rate,
 							  &div, &prate,
 							  &avgrate);
-		if (rate > best_rate && rate <= req->rate) {
+		if (abs(req->rate - rate) < abs(req->rate - best_rate)) {
 			best_parent = parent;
 			best_prate = prate;
 			best_rate = rate;