cmd: sf Drop reassignment of new into flash

cmd: sf Drop reassignment of new into flash

The new pointer points to flash found and that would
assign it to global 'flash' pointer for further flash
operations and also keep track of old flash pointer.

This would happen if the probe is successful or even
failed, but current code assigning new into flash before
and after checking the new.

So, drop the assignment after new checks so flash always
latest new pointer even if probe failed or succeed.

Cc: Simon Glass <sjg@chromium.org>
Cc: Vignesh R <vigneshr@ti.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>