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/Kconfig b/arch/x86/Kconfig
index 5a1e7a5..9d0f502 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -439,7 +439,7 @@
 config GENERATE_ACPI_TABLE
 	bool "Generate an ACPI (Advanced Configuration and Power Interface) table"
 	default n
-	select CMD_QEMU_FW_CFG if QEMU
+	select QFW if QEMU
 	help
 	  The Advanced Configuration and Power Interface (ACPI) specification
 	  provides an open standard for device configuration and management