This change adds MADT entries to the X86Board. Previously, the kernel in full-system mode was complaining about a `ACPI BIOS Error (bug): Invalid table length 0x24 in RSDT/XSDT (20190816/tbutils-291)`. This patch fixes the invalid length and initializes all the tables correctly. Signed-off-by: Kaustav Goswami <kggoswami@ucdavis.edu>