x86: qemu: split qfw command interface and qfw core

This patch splits qfw command interface and qfw core function into two
files, and introduces a new Kconfig option (CONFIG_QFW) for qfw core.

Now when qfw command interface is enabled, it will automatically select
qfw core. This patch also makes the ACPI table generation select
CONFIG_QFW.

Signed-off-by: Miao Yan <yanmiaobest@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/cpu/qemu/Makefile b/arch/x86/cpu/qemu/Makefile
index 43ee4bd..7c08c3d 100644
--- a/arch/x86/cpu/qemu/Makefile
+++ b/arch/x86/cpu/qemu/Makefile
@@ -7,5 +7,6 @@
 ifndef CONFIG_EFI_STUB
 obj-y += car.o dram.o
 endif
-obj-y += cpu.o qemu.o
+obj-y += qemu.o
+obj-$(CONFIG_QFW) += cpu.o
 obj-$(CONFIG_GENERATE_ACPI_TABLE) += acpi_table.o