x86: qemu: fix ACPI Kconfig options

x86: qemu: fix ACPI Kconfig options

CONFIG_GENENRATE_ACPI_TABLE controls the generation of ACPI table which
uses U-Boot's built-in methods and CONFIG_QEMU_ACPI_TABLE controls whether
to load ACPI table from QEMU's fw_cfg interface.

But with commit "697ec431469ce0a4c2fc2c02d8685d907491af84 x86: qemu: Drop
our own ACPI implementation", there is only one way to support ACPI table
for QEMU targets which is the fw_cfg interface. Having two Kconfig options
for this purpose is not necessary any more, so this patch consolidates
the two.

Signed-off-by: Miao Yan <yanmiaobest@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>