xfs_repair: Don't ever try to set the device blocksize

xfs_repair: Don't ever try to set the device blocksize

On 4k devices, we get this warning from repair:

# xfs_repair /dev/sdc2
xfs_repair: warning - cannot set blocksize 512 on block device /dev/sdc2: Invalid argument
Phase 1 - find and verify superblock...
...

but things proceed without trouble after that.

I'm unable to find any history or reason for setting the
device blocksize at the beginning of repair, and in any case,
things clearly work without doing so.  So, let's just remove it.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Alex Elder <aelder@sgi.com>