fix linux build error in osi_probe

Fix a build error for older versions of linux, introduced by
commit 7694f536d3997768b69a635616b0cf24d71a595a
(scsi_command_size became scsi_command_size_tbl)

Fixes a build error on RHEL/CentOS 5.9; 2.6.18-348.3.1.el5.

Change-Id: I7e6f08e7f7cbba47034701e6137eb91fa567dbda
Reviewed-on: http://gerrit.openafs.org/10282
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>