sh: Track the CPU family in sh_cpuinfo.

This adds a family member to struct sh_cpuinfo, which allows us to fall
back more on the probe routines to work out what sort of subtype we are
running on. This will be used by the CPU cache initialization code in
order to first do family-level initialization, followed by subtype-level
optimizations.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>