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/drivers/core/Kconfig b/drivers/core/Kconfig
index 0f755aa..f0d848f 100644
--- a/drivers/core/Kconfig
+++ b/drivers/core/Kconfig
@@ -448,6 +448,7 @@
 
 config ACPIGEN
 	bool "Support ACPI table generation in driver model"
+	depends on ACPI
 	default y if SANDBOX || (GENERATE_ACPI_TABLE && !QEMU)
 	select LIB_UUID
 	help