scsi: simplify scsi_partsize

Call scsi_bios_ptable from scsi_partsize instead of requiring boilerplate
code in the callers.  Also switch the calling convention to match that
of the ->bios_param instances calling this function, and use true/false
for the return value instead of the weird -1 convention.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>