AMD: process leaf 0x7 only if index == 0
AMD: process leaf 0x7 only if index == 0

per AMD EPYC PPR specifications

Signed-off-by: Serban Iorga <4cd75ae1c2f5ea126376f5daa1ce9f5f3016cb24@amazon.com>

firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker