[PARTITION]: Sun/Solaris VTOC table corrections

Start doing VTOC validation before using its contents.
The validation is adjusted so as not to break existing setups
that do not set the VTOC version, sanity and partition count entries.
VTOC tables with more than 8 partitions will NOT be used.

Signed-off-by: Mark Fortescue <mark@mtfhpc.demon.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>