acpi: Create a new Kconfig for ACPI

We have several Kconfig options for ACPI, but all relate to specific
functions, such as generating tables and AML code.

Add a new option which controls including basic ACPI library code,
including the lib/acpi directory. This will allow us to add functions
which are available even if table generation is not supported.

Adjust the command to avoid a build error when ACPIGEN is not enabled.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/lib/acpi/Makefile b/lib/acpi/Makefile
index 956b5a0..12337ab 100644
--- a/lib/acpi/Makefile
+++ b/lib/acpi/Makefile
@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0+
 #
 
+ifdef CONFIG_$(SPL_TPL_)GENERATE_ACPI_TABLE
+
 obj-$(CONFIG_$(SPL_)ACPIGEN) += acpigen.o
 obj-$(CONFIG_$(SPL_)ACPIGEN) += acpi_device.o
 obj-$(CONFIG_$(SPL_)ACPIGEN) += acpi_dp.o
@@ -21,3 +23,5 @@
 obj-y += facs.o
 obj-y += ssdt.o
 endif
+
+endif # GENERATE_ACPI_TABLE