clk: scpi: mark scpi_clk_match as maybe unused

The scpi_clk_match (struct of_device_id) is referenced only with
CONFIG_OF builds thus mark it as __maybe_unused:

    drivers/clk/clk-scpi.c:132:34: warning:
        ‘scpi_clk_match’ defined but not used [-Wunused-const-variable=]
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201103162435.13689-8-krzk@kernel.orgAcked-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/clk-scpi.c

@@ -129,7 +129,7 @@ static const struct clk_ops scpi_dvfs_ops = {
 	.set_rate = scpi_dvfs_set_rate,
 };
 
-static const struct of_device_id scpi_clk_match[] = {
+static const struct of_device_id scpi_clk_match[] __maybe_unused = {
 	{ .compatible = "arm,scpi-dvfs-clocks", .data = &scpi_dvfs_ops, },
 	{ .compatible = "arm,scpi-variable-clocks", .data = &scpi_clk_ops, },
 	{}