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>