arch/x86_64: save MSR_IA32_FEATURE_CONTROL
arch/x86_64: save MSR_IA32_FEATURE_CONTROL

The MSR was previously masked from saving, but this is no longer
relevant.

Signed-off-by: Nikita Kalyazin <c53e872bee32dfab6176fca8e0f6635ed7a871db@amazon.co.uk>

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