ext2: fix unused-but-set variable

This variable was introduced in hrev38573 which is the conclusion of
a GSoC project by jvff to add write support to the ext2 driver.
It has been unused for 13 years, I think it is safe to remove.

Change-Id: I8ae4635dbc39f108b769d90b92e5545f8183a10d
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6715
Reviewed-by: Fredrik Holmqvist <[email protected]>

src/add-ons/kernel/file_systems/ext2/BlockAllocator.cpp

@@ -737,7 +737,6 @@ BlockAllocator::Allocate(Transaction& transaction, Inode* inode,
 		return B_BAD_VALUE;
 
 	uint32 group = inode->ID() / fVolume->InodesPerGroup();
-	uint32 preferred = 0;
 
 	if (inode->Size() > 0) {
 		// Try to allocate near it's last blocks
@@ -797,7 +796,6 @@ BlockAllocator::Allocate(Transaction& transaction, Inode* inode,
 		}
 
 		group = (lastBlock - fFirstBlock) / fBlocksPerGroup;
-		preferred = (lastBlock - fFirstBlock) % fBlocksPerGroup + 1;
 	}
 
 	// TODO: Apply some more policies