ACPI: split CONFIG_ACPI into 4 pieces

ACPI: split CONFIG_ACPI into 4 pieces

As core.c, piix4.c, ich9.c and pcihp.c are for x86, add CONFIG_ACPI_X86
to make it only for x86. ARM doesn't support cpu and memory hotplug, add
CONFIG_ACPI_CPU_HOTPLUG and CONFIG_ACPI_MEMORY_HOTPLUG to exclude them
for target-arm.

Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 1432522520-8068-24-git-send-email-zhaoshenglong@huawei.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>