clk: at91: clk-generated: Limit the requested rate to our range

On clk_generated_determine_rate(), the requested rate could be outside
of clk's range. Limit the rate to the clock's range to not return an
error.

Fixes: df70aeef

 ("clk: at91: add generated clock driver")
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Link: https://lore.kernel.org/r/20210707131213.3283509-1-codrin.ciubotariu@microchip.com
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>