[SPARC64]: Fix system type in /proc/cpuinfo and remove bogus OBP check.

Report 'sun4v' when appropriate in /proc/cpuinfo

Remove all the verifications of the OBP version string.  Just
make sure it's there, and report it raw in the bootup logs and
via /proc/cpuinfo.

Signed-off-by: David S. Miller <davem@davemloft.net>