nvmem: bcm-ocotp: mark ACPI device ID table as maybe unused

"bcm_otpc_acpi_ids" is used with ACPI_PTR, so a build with !CONFIG_ACPI
has a warning:

  drivers/nvmem/bcm-ocotp.c:247:36: error:
    ‘bcm_otpc_acpi_ids’ defined but not used [-Werror=unused-const-variable=]
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20220321110326.44652-1-krzk@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/bcm-ocotp.c

@@ -244,7 +244,7 @@ static const struct of_device_id bcm_otpc_dt_ids[] = {
 };
 MODULE_DEVICE_TABLE(of, bcm_otpc_dt_ids);
 
-static const struct acpi_device_id bcm_otpc_acpi_ids[] = {
+static const struct acpi_device_id bcm_otpc_acpi_ids[] __maybe_unused = {
 	{ .id = "BRCM0700", .driver_data = (kernel_ulong_t)&otp_map },
 	{ .id = "BRCM0701", .driver_data = (kernel_ulong_t)&otp_map_v2 },
 	{ /* sentinel */ }