firmware: arm_sdei: Remove duplicate check in sdei_get_conduit()

The following two checks are duplicate because @acpi_disabled doesn't
depend on CONFIG_ACPI. So the duplicate check (IS_ENABLED(CONFIG_ACPI))
can be dropped. More details is provided to keep the commit log complete:

   * @acpi_disabled is defined in arch/arm64/kernel/acpi.c when
     CONFIG_ACPI is enabled.
   * @acpi_disabled in defined in include/acpi.h when CONFIG_ACPI
     is disabled.
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: James Morse <james.morse@arm.com>
Link: https://lore.kernel.org/r/20200922130423.10173-7-gshan@redhat.comSigned-off-by: Will Deacon <will@kernel.org>

drivers/firmware/arm_sdei.c

@@ -958,7 +958,7 @@ static int sdei_get_conduit(struct platform_device *pdev)
 		}
 
 		pr_warn("invalid \"method\" property: %s\n", method);
-	} else if (IS_ENABLED(CONFIG_ACPI) && !acpi_disabled) {
+	} else if (!acpi_disabled) {
 		if (acpi_psci_use_hvc()) {
 			sdei_firmware_call = &sdei_smccc_hvc;
 			return SMCCC_CONDUIT_HVC;