If this memcmp() is not inlined then PVH early boot code can call
into KASAN-instrumented memcmp() which results in unbootable VMs:
pvh_start_xen
xen_prepare_pvh
xen_cpuid_base
hypervisor_cpuid_base
memcmp
Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>