cpu: Add helper cpu_model_from_type()

cpu: Add helper cpu_model_from_type()

Add helper cpu_model_from_type() to extract the CPU model name from
the CPU type name in two circumstances: (1) The CPU type name is the
combination of the CPU model name and suffix. (2) The CPU type name
is same to the CPU model name.

The helper will be used in the subsequent commits to conver the
CPU type name to the CPU model name.

Suggested-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20231114235628.534334-6-gshan@redhat.com>
[PMD: Mention returned string must be released with g_free()]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>