acpi: Kconfig symbol CONFIG_QFW_ACPI

We have two implementations of write_acpi_tables(). One for writing ACPI
tables based on ACPI_WRITER() entries another based on copying tables from
QEMU.

Create a symbol CONFIG_QFW_ACPI that signifies copying ACPI tables from
QEMU and use it consistently.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/acpi/Makefile b/lib/acpi/Makefile
index c1c9675..cc28684 100644
--- a/lib/acpi/Makefile
+++ b/lib/acpi/Makefile
@@ -12,7 +12,7 @@
 obj-y += acpi_writer.o
 
 # With QEMU the ACPI tables come from there, not from U-Boot
-ifndef CONFIG_QEMU
+ifndef CONFIG_QFW_ACPI
 obj-y += base.o
 obj-y += csrt.o
 obj-y += mcfg.o