libxl/arm: Generate static ACPI DSDT table

libxl/arm: Generate static ACPI DSDT table

It uses static DSDT table like the way x86 uses. Currently the DSDT
table only contains processor device objects and it generates the
maximal objects which so far is 128.

While the GUEST_MAX_VCPUS is defined under __XEN__ or __XEN_TOOLS__, it
needs to add -D__XEN_TOOLS__ to compile mk_dsdt.c.

Also only check iasl for aarch64 in configure since ACPI on ARM32 is not
supported.

Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Acked-by: Julien Grall <julien.grall@arm.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
[ wei: run autogen.sh and fix compilation on x86 ]
Signed-off-by: Wei Liu <wei.liu2@citrix.com>