Documentation: remove reference to ll_rw_blk.c and moved drivers/block/elevator.c

The drivers/block/ll_rw_block.c has been split and organized in the block/ directory, and also drivers/block/elevator.c has been moved to the block/ directory. Update Documentation/block/biodoc.txt accordingly

---

index 4dbb8be..3c5434c 100644
@@ -914,7 +914,7 @@ I/O scheduler, a.k.a. elevator, is implemented in two 

layers. Generic dispatch
queue and specific I/O schedulers. Unless stated otherwise, elevator is used to refer to both parts and I/O scheduler to specific I/O schedulers.

-Block layer implements generic dispatch queue in ll_rw_blk.c and elevator.c. +Block layer implements generic dispatch queue in block/*.c.
The generic dispatch queue is responsible for properly ordering barrier requests, requeueing, handling non-fs requests and all other subtleties.

@@ -926,8 +926,8 @@ be built inside the kernel. Each queue can choose different one and can also
change to another one dynamically.

A block layer call to the i/o scheduler follows the convention elv_xxx().
This
-calls elevator_xxx_fn in the elevator switch (drivers/block/elevator.c). Oh, -xxx and xxx might not match exactly, but use your imagination. If an elevator +calls elevator_xxx_fn in the elevator switch (block/elevator.c). Oh, xxx +and xxx might not match exactly, but use your imagination. If an elevator
doesn't implement a function, the switch does nothing or some minimal house keeping work.