xen/arm: gic: acpi: Use the correct length for the GICC structure

xen/arm: gic: acpi: Use the correct length for the GICC structure

The length of the GICC structure in the MADT ACPI table differs between
version 5.1 and 6.0, although there are no other relevant differences.

Use the BAD_MADT_GICC_ENTRY macro, which was specifically designed to
overcome this issue.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>