clk: at91: Mark struct clk_range as const

It's just some static data that doesn't get changed after being used.
Mark it const everywhere.

Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/at91/sama5d2.c

@@ -16,7 +16,7 @@ static u8 plla_out[] = { 0 };
 
 static u16 plla_icpll[] = { 0 };
 
-static struct clk_range plla_outputs[] = {
+static const struct clk_range plla_outputs[] = {
 	{ .min = 600000000, .max = 1200000000 },
 };