sparc: make cpu feature parsing property based

sparc: make cpu feature parsing property based

with features converted to properties we can use the same
approach as x86 for features parsing and drop legacy
approach that manipulated CPU instance directly.
New sparc_cpu_parse_features() will allow only +-feat
and explicitly disable feat=on|off syntax for now.

With that in place and sparc_cpu_parse_features() providing
generic CPUClass::parse_features callback, the cpu_sparc_init()
will do the same job as cpu_generic_init() so replace content
of cpu_sparc_init() with it.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Acked-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <1503672460-109436-1-git-send-email-imammedo@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>