[PATCH] ext4: rename logic_sb_block

I assume this means "logical sb block".  So call it that.

I still don't understand the name though.  A block is a block.  What's
different about this one?

Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>