cpu_x86: Allow multiple signatures for a CPU model

cpu_x86: Allow multiple signatures for a CPU model

CPU signatures in the cpu_map serve as a hint for CPUID to CPU model
matching algorithm. If the CPU signatures matches any CPU model in the
cpu_map, this model will be the preferred one.

This works out well and solved several mismatches, but in real world
CPUs which should match a single CPU model may be produced with several
different signatures. For example, low voltage Broadwell CPUs for
laptops and Broadwell CPUs for servers differ in CPU model numbers while
we should detect them all as Broadwell CPU model.

This patch adds support for storing several signatures for a single CPU
model to make this hint useful for more CPUs. Later commits will provide
additional signatures for existing CPU models, which will correct some
results in our CPU test suite.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>