loop: remove redundant initialization of pointer node

loop: remove redundant initialization of pointer node

The pointer node is being initialized with a value that is never
read, it is being re-assigned the same value a little futher on.
Remove the redundant initialization. Cleans up clang scan warning:

drivers/block/loop.c:823:19: warning: Value stored to 'node' during
its initialization is never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20220113001432.1331871-1-colin.i.king@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>