clk: allow building lan966x as a module

Set the COMMON_CLK_LAN966X option as a tristate and switch from
builtin_platform_driver() to module_platform_driver() to allow building
and using this driver as a module.
Signed-off-by: Clément Léger <clement.leger@bootlin.com>
Link: https://lore.kernel.org/r/20220617103306.489466-1-clement.leger@bootlin.comSigned-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/Kconfig

@@ -249,7 +249,7 @@ config COMMON_CLK_GEMINI
 	  platform, also known as SL3516 or CS3516.
 
 config COMMON_CLK_LAN966X
-	bool "Generic Clock Controller driver for LAN966X SoC"
+	tristate "Generic Clock Controller driver for LAN966X SoC"
 	depends on HAS_IOMEM
 	depends on OF
 	depends on SOC_LAN966 || COMPILE_TEST

drivers/clk/clk-lan966x.c

@@ -286,7 +286,7 @@ static struct platform_driver lan966x_clk_driver = {
 		.of_match_table = lan966x_clk_dt_ids,
 	},
 };
-builtin_platform_driver(lan966x_clk_driver);
+module_platform_driver(lan966x_clk_driver);
 
 MODULE_AUTHOR("Kavyasree Kotagiri <kavyasree.kotagiri@microchip.com>");
 MODULE_DESCRIPTION("LAN966X clock driver");