[cpuid] Allow hypervisor CPUID leaves to be accessed as settings

[cpuid] Allow hypervisor CPUID leaves to be accessed as settings

Redefine bit 30 of an SMBIOS numerical setting to be part of the
function number, in order to allow access to hypervisor CPUID leaves.

This technically breaks backwards compatibility with scripts
attempting to read more than 64 consecutive functions.  Since there is
no meaningful block of 64 consecutive related functions, it is
vanishingly unlikely that this capability has ever been used.

Signed-off-by: Michael Brown <mcb30@ipxe.org>