clk: meson: a1: Staticize rtc clk

Sparse rightly complains that this symbol is supposed to be static.

Cc: Jian Hu <jian.hu@amlogic.com>
Cc: Dmitry Rokosov <ddrokosov@sberdevices.ru>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Fixes: 84af914 ("clk: meson: a1: add Amlogic A1 Peripherals clock controller driver")
Link: https://lore.kernel.org/r/20230612182332.371003-1-sboyd@kernel.org
Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Author: bebarino

drivers/clk/meson/a1-peripherals.c

@@ -218,7 +218,7 @@ static struct clk_regmap rtc_32k_sel = {
 	},
 };
 
-struct clk_regmap rtc = {
+static struct clk_regmap rtc = {
 	.data = &(struct clk_regmap_gate_data){
 		.offset = RTC_BY_OSCIN_CTRL0,
 		.bit_idx = 30,