vinum_bounds_check: Don't check the label sector if the architecture doesn't have one.  The test was bogus on these architectures, but recent changes broke it altogether.
vinum_bounds_check: Don't check the label sector if the architecture
doesn't have one.  The test was bogus on these architectures, but
recent changes broke it altogether.

Prompted by:  phk

This should fix the recent SPARC 64 build problems.

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase