clk: at91: clk-generated: check best_rate against ranges

Check best_rate against available clock ranges.

Fixes: df70aeef ("clk: at91: add generated clock driver")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/1595403506-8209-3-git-send-email-claudiu.beznea@microchip.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>